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diff --git a/old/56315-0.txt b/old/56315-0.txt deleted file mode 100644 index a1fc1a4..0000000 --- a/old/56315-0.txt +++ /dev/null @@ -1,7521 +0,0 @@ -The Project Gutenberg EBook of Texas Fossils: An Amateur Collector's -Handbook, by William H. Matthews III - -This eBook is for the use of anyone anywhere in the United States and most -other parts of the world at no cost and with almost no restrictions -whatsoever. You may copy it, give it away or re-use it under the terms of -the Project Gutenberg License included with this eBook or online at -www.gutenberg.org. If you are not located in the United States, you'll have -to check the laws of the country where you are located before using this ebook. - -Title: Texas Fossils: An Amateur Collector's Handbook - Texas Bureau of Economic Geology Guidebook 2 - -Author: William H. Matthews III - -Release Date: January 5, 2018 [EBook #56315] - -Language: English - -Character set encoding: UTF-8 - -*** START OF THIS PROJECT GUTENBERG EBOOK TEXAS FOSSILS *** - - - - -Produced by Stephen Hutcheson, MFR and the Online -Distributed Proofreading Team at http://www.pgdp.net - - - - - - - BUREAU OF ECONOMIC GEOLOGY - The University of Texas at Austin - Austin, Texas 78712 - John T. Lonsdale, Director - - - Guidebook 2 - - - - - TEXAS FOSSILS: - _An Amateur Collector’s Handbook_ - - - By - William H. Matthews III - - November 1960 - _Second Printing, July 1963_ - _Third Printing, August 1967_ - _Fourth Printing, June 1971_ - _Fifth Printing, November 1973_ - _Sixth Printing, April 1976_ - _Seventh Printing, November 1978_ - _Eighth Printing, September 1981_ - _Ninth Printing, August 1984_ - - - - - Contents - - - Page - Introduction 1 - What are fossils? 3 - The study of fossils 4 - Paleobotany 4 - Invertebrate paleontology 4 - Vertebrate paleontology 4 - Micropaleontology 4 - Preservation of fossils 5 - Requirements of fossilization 5 - Missing pages in the record 5 - Different kinds of fossil preservation 7 - Original soft parts of organisms 7 - Original hard parts of organisms 7 - Calcareous remains 10 - Phosphatic remains 10 - Siliceous remains 10 - Chitinous remains 10 - Altered hard parts of organisms 10 - Carbonization 10 - Petrifaction or permineralization 10 - Replacement or mineralization 10 - Replacement by calcareous material 11 - Replacement by siliceous material 11 - Replacement by iron compounds 11 - Traces of organisms 11 - Molds and casts 11 - Tracks, trails, and burrows 14 - Coprolites 14 - Gastroliths 14 - Pseudofossils 14 - Dendrites 14 - Slickensides 16 - Concretions 16 - Where and how to collect fossils 17 - Collecting equipment 17 - Where to look 19 - How to collect 20 - Cleaning and preparation of fossils 21 - How fossils are named 21 - The science of classification 21 - The units of classification 22 - Identification of fossils 23 - Use of identification keys 23 - Identification key to main types of invertebrate fossils 26 - List of Texas colleges offering geology courses 27 - Cataloging the collection 31 - How fossils are used 31 - Geologic history 33 - Geologic column and time scale 33 - The geology of Texas 34 - Physiography 35 - Trans-Pecos region 35 - Texas Plains 35 - High Plains 35 - North-central Plains 37 - Edwards Plateau 37 - Grand Prairie 37 - Llano uplift 37 - Gulf Coastal Plain 37 - Geology 37 - Precambrian rocks 40 - Paleozoic rocks 40 - Cambrian 40 - Ordovician 40 - Silurian 40 - Devonian 40 - Mississippian 41 - Pennsylvanian 41 - Permian 41 - Mesozoic rocks 42 - Triassic 42 - Jurassic 42 - Cretaceous 42 - Cenozoic rocks 43 - Tertiary 43 - Quaternary 43 - Main types of fossils 44 - Plant fossils 44 - Classification of the plant kingdom 44 - Division Thallophyta 44 - Division Bryophyta 44 - Division Tracheophyta 44 - Animal fossils 48 - Phylum Protozoa 48 - Class Sarcodina 48 - Order Foraminifera 48 - Order Radiolaria 48 - Phylum Porifera 49 - Phylum Coelenterata 49 - Class Anthozoa 49 - Subclass Zoantharia 50 - Order Rugosa 50 - Order Scleractinia 50 - Order Tabulata 50 - Phylum Bryozoa 50 - Phylum Brachiopoda 54 - Class Inarticulata 54 - Class Articulata 56 - Phylum Mollusca 56 - Class Gastropoda 59 - Class Pelecypoda 59 - Class Cephalopoda 66 - Subclass Nautiloidea 66 - Subclass Ammonoidea 75 - Subclass Coleoidea 78 - Order Belemnoidea 78 - Phylum Annelida 78 - Phylum Arthropoda 78 - Subphylum Trilobitomorpha 78 - Class Trilobita 78 - Subphylum Crustacea 80 - Class Ostracoda 80 - Phylum Echinodermata 80 - Subphylum Pelmatozoa 81 - Class Cystoidea 81 - Class Blastoidea 81 - Class Crinoidea 81 - Subphylum Eleutherozoa 82 - Class Asterozoa 82 - Subclass Asteroidea 82 - Subclass Ophiuroidea 82 - Class Echinozoa 82 - Subclass Echinoidea 82 - Subclass Holothuroidea 85 - Phylum Chordata 85 - Subphylum Hemichordata 85 - Class Graptolithina 85 - Subphylum Vertebrata 86 - Superclass Pisces 87 - Class Agnatha 87 - Class Placodermi 87 - Class Chondrichthyes 87 - Class Osteichthyes 87 - Superclass Tetrapoda 89 - Class Amphibia 89 - Class Reptilia 89 - Cotylosaurs 89 - Turtles 89 - Pelycosaurs 89 - Therapsids 89 - Ichthyosaurs 95 - Mosasaurs 95 - Plesiosaurs 95 - Phytosaurs 95 - Crocodiles and alligators 95 - Pterosaurs 95 - Dinosaurs 95 - Order Saurischia 97 - Suborder Theropoda 97 - Suborder Sauropoda 97 - Order Ornithischia 97 - Suborder Ornithopoda 97 - Suborder Stegosauria 97 - Suborder Ankylosauria 97 - Suborder Ceratopsia 100 - Class Aves 100 - Class Mammalia 100 - Subclass Allotheria 100 - Subclass Theria 100 - Order Edentata 100 - Order Carnivora 102 - Order Pantodonta 102 - Order Dinocerata 102 - Order Proboscidea 102 - Order Perissodactyla 104 - Horses 104 - Titanotheres 104 - Chalicotheres 106 - Rhinoceroses 106 - Order Artiodactyla 106 - Entelodonts 106 - Camels 106 - Books about fossils 108 - General works 108 - Nontechnical and juvenile 108 - Collecting helps 108 - Reference works 109 - Selected references on Texas fossils 109 - Glossary 111 - Index 115 - - - - - Illustrations - - - Figures— Page - 1. Sketch of a coprolite—fossilized animal excrement 14 - 2. Sketch of a gastrolith—the gizzard stone of an ancient - reptile 14 - 3. Dendrites—a typical pseudofossil 14 - 4. Types of symmetry in a fossil coral 24 - 5. Bilateral symmetry in fossil brachiopod 24 - 6. A brachiopod showing specimen number and accompanying label 31 - 7. Two types of micropaleontological slides 32 - 8. Typical Pennsylvanian crinoidal limestone 41 - 9. Typical Texas Foraminifera 49 - 10. Typical radiolarians 49 - 11. Morphology and principal parts of corals 50 - 12. Two types of bryozoans 50 - 13. Morphology and principal parts of articulate brachiopods 54 - 14. _Lingula_, a typical inarticulate brachiopod 56 - 15. _Kingena wacoensis_, a common Cretaceous brachiopod 56 - 16. Morphology and principal parts of gastropod shells 60 - 17. Morphology and principal parts of a typical pelecypod shell 65 - 18. Morphology and principal parts of the pearly nautilus 75 - 19. Characteristic features of the various types of cephalopod - sutures 75 - 20. Types of typical fossil annelid worms 78 - 21. Morphology and principal parts of trilobites 80 - 22. Two extinct attached echinoderms, _Pentremites_ and - _Caryocrinites_ 81 - 23. Typical modern crinoid, or “sea lily,” showing principal - parts 81 - 24. Graptolites 86 - 25. Sketches of mastodon and mammoth teeth 104 - 26. Two views of a typical fossil horse tooth 104 - - - Plates— Page - 1. Geologic time scale Frontispiece - 2. Types of fossil preservation 8 - 3. Silicified brachiopods dissolved from Permian limestones of the - Glass Mountains, Brewster County, Texas 12 - 4. Dinosaur tracks in limestone in bed of Paluxy Creek near Glen - Rose, Somervell County, Texas 15 - 5. Fossil collecting equipment 18 - 6-8. Fossil identification charts 28-30 - 9. Physiographic map of Texas 36 - 10. Geologic map of Texas 38-39 - 11. Geologic range of the major groups of plants and animals 45 - 12. Fossil plants—thallophytes and tracheophytes 46 - 13. Fossil plants—tracheophytes 47 - 14. Paleozoic sponges and sponge spicules 51 - 15. Pennsylvanian corals 52 - 16. Cretaceous and Tertiary corals 53 - 17. Pennsylvanian bryozoans and Cambrian and Mississippian - brachiopods 55 - 18, 19. Pennsylvanian brachiopods 57, 58 - 20. Pennsylvanian gastropods 61 - 21. Pennsylvanian and Cretaceous gastropods 62 - 22, 23. Tertiary gastropods 63, 64 - 24. Pennsylvanian pelecypods 67 - 25-28. Cretaceous pelecypods 68-71 - 29-31. Tertiary pelecypods 72-74 - 32. Pennsylvanian and Cretaceous cephalopods 76 - 33. Cretaceous cephalopods 77 - 34. Fossil arthropods 79 - 35. Fossil starfishes, crinoids, and holothurian sclerites 83 - 36. Cretaceous echinoids 84 - 37. Primitive armored fish, shark teeth, and conodonts 88 - 38. Comparison of the dinosaurs 90 - 39. Comparison of Mesozoic flying and swimming reptiles 91 - 40. Pelycosaur, cotylosaur, and a primitive amphibian 92 - 41. Swimming reptiles 93 - 42. Phytosaur and flying dinosaurs 94 - 43. Skull of _Phobosuchus_, from Cretaceous of Trans-Pecos Texas - 96 - 44. Saurischian dinosaurs 98 - 45. Ornithischian dinosaurs 99 - 46, 47. Cenozoic mammals 101, 103 - 48. Tertiary mammals 105 - 49. Cenozoic mammals 107 - - [Illustration: Plate 1 - GEOLOGIC TIME SCALE] - - ERA - PERIOD - EPOCH - CHARACTERISTIC LIFE - CENOZOIC “Recent Life” - QUATERNARY 1 MILLION YEARS - Recent - Pleistocene - TERTIARY 64 MILLION YEARS - Pliocene - Miocene - Oligocene - Eocene - Paleocene - MESOZOIC “Middle Life” - CRETACEOUS 70 MILLION YEARS - JURASSIC 45 MILLION YEARS - TRIASSIC 50 MILLION YEARS - PALEOZOIC “Ancient Life” - PERMIAN 55 MILLION YEARS - CARBONIFEROUS - PENNSYLVANIAN 30 MILLION YEARS - MISSISSIPPIAN 35 MILLION YEARS - DEVONIAN 55 MILLION YEARS - SILURIAN 20 MILLION YEARS - ORDOVICIAN 75 MILLION YEARS - CAMBRIAN 100 MILLION YEARS - PRECAMBRIAN ERAS - PROTEROZOIC ERA - ARCHEOZOIC ERA - APPROXIMATE AGE OF THE EARTH MORE THAN 3 BILLION 300 MILLION YEARS - - - - - Texas Fossils - An Amateur Collector’s Handbook - - - William H. Matthews III[1] - - - - - INTRODUCTION - - -Almost everyone has seen the fossilized remains of prehistoric plants or -animals. These might have been the skeleton of a gigantic dinosaur, the -petrified trunk of an ancient tree, or the shells of snails or oysters -that lived in the great seas that covered Texas millions of years ago. - -Each year more and more people are learning that these fossils are more -than mere curiosities. Instead, they are realizing that a good -collection of fossils provides much information about the early history -of our earth, and that fossil collecting can be a most enjoyable, -fascinating, and rewarding hobby. It is for these people that _Texas -Fossils_ was written. - -This publication is primarily an amateur collector’s handbook and as -such offers many suggestions and aids to those who would pursue the -hobby of fossil collecting. It tells, for example, what fossils are, -where and how to collect them, and how they are used. Suggestions are -made as to how the specimens may be identified and catalogued, and there -are discussions and illustrations of the main types of plant and animal -fossils. Included also is a simplified geologic map of Texas and a brief -review of the geology of the State. - -_Texas Fossils_ is not a comprehensive study of the paleontology of -Texas. Rather, it deals primarily with the more common species that the -average collector is likely to find. These fossils are illustrated in -the plates and figures, and these illustrations should be of some help -in identifying the specimens in one’s collection. Included for -completeness, however, are sketches and descriptions of some of the more -rare and unusual fossils, and, for general interest, there are -illustrations and descriptions of many of the extinct reptiles and -mammals that once inhabited this State. - -In addition, a group of selected references has been included for the -reader who wishes to know more about earth history and paleontology. -Many of these publications provide references of a more technical nature -for the more advanced or serious collector, and some of them list -excellent collecting localities. - -A minimum of technical terminology has been used, but terms not commonly -found in dictionaries, or which have not been explained in the text, are -defined in the glossary (pp. 111-114). - -Many people have helped in the planning, preparation, and completion of -_Texas Fossils_, and their help is gratefully acknowledged: Dr. Keith -Young, The University of Texas; Dr. Harold Beaver, Baylor University; -and Professor Jack Boon, Arlington State College, offered helpful -suggestions and information on Cretaceous fossils; Professors Richmond -L. Bronaugh, Baylor University, and Jack T. Hughes, West Texas State -College, provided information on vertebrate collecting localities; -Professor Fred Smith, Texas A&M College, supplied data on Tertiary -collecting localities and fossils which were used in illustrations; Dr. -Saul Aronow and Professor Darrell Davis, Lamar State College of -Technology; Dr. Jules DuBar, University of Houston; and Dr. Samuel P. -Ellison, The University of Texas, made valuable suggestions which have -been incorporated into the manuscript. - -Special thanks are due Drs. John T. Lonsdale, L. F. Brown, Jr., and -Peter U. Rodda, Bureau of Economic Geology, who critically read the -manuscript and contributed greatly to the presentation of the material; -Dr. John A. Wilson, The University of Texas, who read the section on -vertebrate fossils and made invaluable suggestions and criticisms; Miss -Josephine Casey, who edited the manuscript; and Mr. J. W. Macon, who -prepared the maps and charts. - -Thanks are due also to Dr. G. A. Cooper, United States National Museum, -who prepared Plate 3 especially for this publication, and to R. T. Bird -and the American Museum of Natural History for photographs used in -Plates 4 and 43. Plates 38 and 39 were provided through the courtesy of -Dr. J. W. Dixon, Jr., and the Geology Department of Baylor University. -The other photographs were prepared by the writer. To Sarah Louise -Wilson, Lamar State College of Technology, the writer gratefully -acknowledges her tireless and painstaking efforts in preparing the many -fine drawings which make up the balance of the illustrations. - - - - - WHAT ARE FOSSILS? - - -_Fossils are the remains or evidence of ancient plants or animals that -have been preserved in the rocks of the earth’s crust._ Most fossils -represent the preservable hard parts of some prehistoric organism that -once lived in the area in which the remains were collected. - -The word fossil is derived from the Latin word _fossilis_, meaning “dug -up,” and for many years any unusual object dug out of the ground was -considered to be a “fossil.” For this reason some of the earlier books -dealing with fossils include discussions of rocks, minerals, and other -inorganic objects. - -There is much evidence to indicate that man has been interested in -fossils since the very earliest times, and fossil shells, bones, and -teeth have been found associated with the remains of primitive and -prehistoric men. It is quite possible that the owners of these objects -believed that they possessed supernatural powers, such as healing -properties or the ability to remove curses. - -During the earliest periods of recorded history, certain Greek scholars -found the remains of fish and sea shells in desert and mountainous -regions. These men were greatly puzzled by the occurrence of these -objects at such great distances from the sea, and some of them devoted -considerable time to an explanation of their presence. - -In 450 B.C., Herodotus noticed fossils in the Egyptian desert and -correctly concluded that the Mediterranean Sea had once been in that -area. - -Aristotle in 400 B.C. stated that fossils were organic in origin but -that they were embedded in the rocks as a result of mysterious plastic -forces at work within the earth. One of his students, Theophrastus -(about 350 B.C.), also believed that fossils represented some form of -life but thought that they had developed from seeds or eggs that had -been planted in the rocks. - -Strabo (about 63 B.C. to A.D. 20) was another important Greek scholar -who attempted to explain the presence of fossils. He noted the -occurrence of marine fossils well above sea level and correctly inferred -that the rocks containing them had been subjected to considerable -elevation. - -During the “Dark Ages” fossils were alternately explained as freaks of -nature, the remains of attempts at special creation, and devices of the -devil which had been placed in the rocks to lead men astray. These -superstitious beliefs and the opposition from religious authorities -hindered the study of fossils for hundreds of years. - -In approximately the middle of the fifteenth century the true origin of -fossils was generally accepted, and they were considered to be the -remains of prehistoric organisms which had been preserved in the earth’s -crust. With the definite recognition of fossils as organic remains, many -of the more primitive theories were discarded for one just as -impractical—these remains were considered remnants of the Great Flood as -recorded in the Scriptures. The resulting controversy between scientists -and theologians lasted for about 300 years. - -During the Renaissance several of the early natural scientists concerned -themselves with investigations of fossils. Noteworthy among these was -Leonardo da Vinci, the famous Italian artist, naturalist, and engineer. -Leonardo insisted that the Flood could not be responsible for all -fossils nor for their occurrence in the highest mountains. He reaffirmed -the belief that fossils were indisputable evidence of ancient life, and -that the sea had once covered northern Italy. Leonardo explained that -the remains of the animals that had inhabited this ancient body of water -were buried in the sediments of the sea floor, and that at some later -date in earth history this ocean bottom was elevated well above sea -level to form the Italian peninsula. - -In the late eighteenth and early nineteenth centuries the study of -fossils became firmly established as a science, and since that time -fossils have become increasingly important to the geologist. - - - - - THE STUDY OF FOSSILS - - -The study of fossils is called _paleontology_ (Greek _palaios_, ancient; -_ontos_, a being; _logos_, word or discourse). Information gathered with -the help of paleontology has greatly increased the knowledge of ancient -plants and animals and of the world in which they lived. - -Fossils represent the remains of such great numbers and various types of -organisms that paleontologists have found it helpful to establish four -main divisions within their science. - - - Paleobotany - -Paleobotany deals with the study of fossil plants and the record of the -changes which they have undergone. - - - Invertebrate Paleontology - -This is the study of fossil animals without a backbone or spinal column. -These include such forms as fossil protozoans (tiny one-celled animals), -snails, clams, starfish, and worms, and usually represent the remains of -animals that lived in prehistoric seas. - -Because invertebrate remains are the most common fossils in Texas, this -book is devoted largely to the discussion of invertebrate fossils and -their method of collection. - - - Vertebrate Paleontology - -The vertebrate paleontologist studies the fossils of animals which -possessed a backbone or spinal column. The remains of fish, amphibians, -reptiles, birds, and mammals are typical vertebrate fossils. - - - Micropaleontology - -Micropaleontology is the study of fossils that are so small that they -are best studied under a microscope. These tiny remains are called -microfossils and usually represent the shells or fragments of minute -plants or animals. Because of their small size, microfossils can be -brought out of wells without being damaged by the mechanics of drilling -or coring. For this reason microfossils are particularly valuable to the -petroleum geologist who uses them to identify rock formations thousands -of feet below the surface. - - - - - PRESERVATION OF FOSSILS - - -The majority of fossils are found in marine _sedimentary rocks._ These -are rocks that were formed when salt-water sediments, such as limy muds, -sands, or shell beds, were compressed and cemented together to form -rocks. Only rarely do fossils occur in igneous and metamorphic rocks. -The _igneous rocks_ were once hot and molten and had no life in them, -and _metamorphic rocks_ have been so greatly changed or distorted that -any fossils that were present in the original rock have usually been -destroyed or so altered as to be of little use to the paleontologist. - -But even in the sedimentary rocks only a minute fraction of prehistoric -plants and animals have left any record of their existence. This is not -difficult to understand in view of the rather rigorous requirements of -fossilization. - - - - - REQUIREMENTS OF FOSSILIZATION - - -Although a large number of factors ultimately determine whether an -organism will be fossilized, the three basic requirements are: - -1. _The organism should possess hard parts._ These might be shell, bone, -teeth, or the woody tissue of plants. However, under very favorable -conditions of preservation it is possible for even such fragile material -as an insect or a jellyfish to become fossilized. - -2. _The organic remains must escape immediate destruction after death._ -If the body parts of an organism are crushed, decayed, or badly -weathered, this may result in the alteration or complete destruction of -the fossil record of that particular organism. - -3. _Rapid burial in a material capable of retarding decomposition._ The -type of material burying the remains usually depends upon where the -organism lived. The remains of marine animals are common as fossils -because they fall to the sea floor after death, and here they are -covered by soft muds which will be the shales and limestones of later -geologic periods. The finer sediments are less likely to damage the -remains, and certain fine-grained Jurassic limestones in Germany have -faithfully preserved such delicate specimens as birds, insects, and -jellyfishes. - -Ash falling from nearby volcanoes has been known to cover entire -forests, and some of these fossil forests have been found with the trees -still standing and in an excellent state of preservation. - -Quicksand and tar are also commonly responsible for the rapid burial of -animals. The tar acts as a trap to capture the beasts and as an -antiseptic to retard the decomposition of their hard parts. The Rancho -La Brea tar pit at Los Angeles, California, is famous for the large -number of fossil bones that have been recovered from it. These include -such forms as the sabre-tooth cat, giant ground sloths, and other -creatures that are now extinct. The remains of certain animals that -lived during the Ice Ages have been incorporated into the ice or frozen -ground, and some of these frozen remains are famous for their remarkable -degree of preservation. - - - - - MISSING PAGES IN THE RECORD - - -Although untold numbers of organisms have lived on the earth in past -ages, only a minute fraction of these have left any record of their -existence. Even if the basic requirements of fossilization have been -fulfilled, there are still other reasons why some fossils may never be -found. - -For example, large numbers of fossils have been destroyed by erosion or -their hard parts have been dissolved by underground waters. Others were -entombed in rocks that were later subjected to great physical change, -and fossils enclosed in these rocks are usually so damaged as to be -unrecognizable. - -Then, too, many fossiliferous rocks cannot be studied because they are -covered by water or great thicknesses of sediments, and still others are -situated in places that are geographically inaccessible. These and many -other problems confront the paleontologist as he attempts to catalog the -plants and animals of the past. - -The missing pages in the fossil record become more obvious and more -numerous in the older rocks of the earth’s crust. This is because the -more ancient rocks have had more time to be subjected to physical and -chemical change or to be removed by erosion. - - - - - DIFFERENT KINDS OF FOSSIL PRESERVATION - - -There are many different ways in which plants and animals may become -fossilized. The method of preservation is usually dependent upon (1) the -original composition of the organism, (2) where it lived, and (3) the -forces that affected it after death. - -Most paleontologists recognize four major types of preservation, each -being based upon the composition of the remains or the changes which -they have undergone. - - - - - ORIGINAL SOFT PARTS OF ORGANISMS - - -This type of fossil is formed only under very special conditions of -preservation. To be preserved in this manner, the organism must be -buried in a medium capable of retarding decomposition of the soft parts. -Materials that have been known to produce this type of fossilization are -frozen soil or ice, oil-saturated soils, and amber (fossil resin). It is -also possible for organic remains to become so desiccated that a natural -mummy is formed. This usually occurs only in arid or desert regions and -when the remains have been protected from predators and scavengers. - -Probably the best-known examples of preserved soft parts of fossil -animals have been discovered in Alaska and Siberia. The frozen tundra of -these areas has yielded the remains of large numbers of frozen -mammoths—a type of extinct elephant (Pl. 49). Many of these huge beasts -have been buried for as long as 25,000 years, and their bodies are -exposed as the frozen earth begins to thaw. Some of these giant -carcasses have been so well preserved that their flesh has been eaten by -dogs and their tusks sold by ivory traders. Many museums display the -original hair and skin of these elephants, and some have parts of the -flesh and muscle preserved in alcohol. - -Original soft parts have also been recovered from oil-saturated soils in -eastern Poland. These deposits yielded the well-preserved nose-horn, a -foreleg, and part of the skin of an extinct rhinoceros. - -The natural mummies of ground sloths have been found in caves and -volcanic craters in New Mexico and Arizona. The extremely dry desert -atmosphere permitted thorough dehydration of the soft parts before decay -set in, and specimens with portions of the original skin, hair, tendons, -and claws have been discovered. - -One of the more interesting and unusual types of fossilization is -preservation in amber. This type of preservation was made possible when -ancient insects were trapped in the sticky gum that exuded from certain -coniferous trees. With the passing of time this resin hardened, leaving -the insect encased in a tomb of amber, and some insects and spiders have -been so well preserved that even fine hairs and muscle tissues may be -studied under the microscope. - -Although the preservation of original soft parts has produced some -interesting and spectacular fossils, this type of fossilization is -relatively rare, and the paleontologist must usually work with remains -that have been preserved in stone. - - - - - ORIGINAL HARD PARTS OF ORGANISMS - - -Almost all plants and animals possess some type of hard parts which are -capable of becoming fossilized. Such hard parts may consist of the shell -material of clams, oysters, or snails, the teeth or bones of -vertebrates, the exoskeletons of crabs, or the woody tissue of plants. -These hard parts are composed of various minerals which are capable of -resisting weathering and chemical action, and fossils of this sort are -relatively common. - -Many of the fossil mollusks found in the Tertiary and Cretaceous rocks -of Texas have been preserved in this manner. In some of the specimens -the original shell material is so well preserved that the iridescent -mother-of-pearl layer of the shell is found virtually intact. This type -of preservation is less common, however, in the older rocks of the -State. - - [Illustration: PLATE 2 - Types of Fossil Preservation] - - Figures— - 1. Internal mold of a Texas Cretaceous ammonite (×½). - 2. Internal and external molds of gastropods and pelecypods in Cedar - Park limestone member of the Walnut clay of Comanchean age - (×½). Specimen from quarry near Cedar Park, Williamson County, - Texas. - 3. Internal mold of a Texas Cretaceous pelecypod (×½). - 4. Fossil worm tubes on mold of a Cretaceous ammonite (×½). - 5. Petrified or permineralized mammal bone of Tertiary age (×½). - 6. Internal mold (steinkern) of a typical Texas Cretaceous gastropod - (×½). - 7. Carbon residue of a Tertiary fish (×¼). - -At certain localities in north and central Texas the Woodbine sands of -Upper Cretaceous age (geologic time scale and geologic map, Pls. 1, 10) -contain large numbers of shark and fish teeth (Pl. 37), fish scales and -vertebrae. The remains of these vertebrates are unusually well preserved -and are prized by both amateur and professional collectors. - - - Calcareous Remains - -Hard parts composed of calcite (calcium carbonate) are very common among -the invertebrates. This is particularly true of the shells of clams, -snails, and corals. Many of these shells have been preserved with little -or no evidence of physical change (Pl. 2). - - - Phosphatic Remains - -The bones and teeth of vertebrates and the exoskeletons of many -invertebrates contain large amounts of calcium phosphate. Because this -compound is particularly weather resistant, many phosphatic remains -(such as the fish teeth in the Woodbine sands) are found in an excellent -state of preservation. - - - Siliceous Remains - -Many organisms having skeletal elements composed of silica (silicon -dioxide) have been preserved with little observable change. The -siliceous hard parts of many microfossils and certain types of sponges -have become fossilized in this manner (Pl. 14). - - - Chitinous Remains - -Some organisms have an exoskeleton (outer body covering) composed of -chitin, a material that is similar to finger nails. The fossilized -chitinous exoskeletons of arthropods and other organisms are commonly -preserved as thin films of carbon because of their chemical composition -and method of burial. - - - - - ALTERED HARD PARTS OF ORGANISMS - - -The original hard parts of an organism normally undergo great change -after burial. These changes take place in many ways, but the type of -alteration is usually determined by the composition of the hard parts -and where the organism lived. Some of the more common processes of -alteration are discussed below. - - - Carbonization - -This process, known also as distillation takes place as organic matter -slowly decays after burial. During the process of decomposition, the -organic matter gradually loses its gases and liquids leaving only a thin -film of carbonaceous material (Pl. 2, fig. 7). This is the same process -by which coal is formed, and large numbers of carbonized plant fossils -have been found in many coal deposits. - -In Texas the carbonized remains of plants, fish, and certain -invertebrates have been preserved in this manner, and some of these -carbon residues have accurately recorded even the most minute structures -of these organisms. - - - Petrifaction or Permineralization - -Many fossils have been permineralized or petrified—literally turned to -stone. This type of preservation occurs when mineral-bearing ground -waters infiltrate porous bone, shell, or plant material. These -underground waters deposit their mineral content in the empty spaces of -the hard parts making them heavier and more resistant to weathering. -Some of the more common minerals deposited in this manner are calcite, -silica, and various compounds of iron. - - - Replacement or Mineralization - -This type of preservation takes place when the original hard parts of -organisms are removed after being dissolved by underground water. This -is accompanied by almost simultaneous deposition of other substances in -the resulting voids. Some replaced fossils will have the original -structure destroyed by the replacing minerals. Others, as in the case of -certain silicified tree trunks, may be preserved in minute detail. - -Although more than 50 minerals have been known to replace original -organic structures, the most frequent replacing substances are calcite, -dolomite (a calcium magnesium carbonate), silica, and certain iron -compounds. - - Replacement by calcareous material - -Calcareous replacement occurs when the hard parts of an organism are -replaced by calcite, dolomite, or aragonite (a mineral which is composed -of calcium carbonate but which is less stable than calcite). The -exoskeletons of many corals, echinoderms, brachiopods, and mollusks have -been replaced in this manner. - - Replacement by siliceous material - -When the original organic hard parts have been replaced by silica the -fossil is said to have undergone silicification, and this type of -replacement often produces a very high degree of preservation. This is -particularly true of the silicified Permian (geologic time scale, Pl. 1) -fossils from the Glass Mountains in Brewster County. These fossils are -embedded in limestone which must be dissolved in vats of acid, and after -the enclosing rock has been dissolved the residue yields an amazing -variety of perfectly preserved invertebrate fossils (Pl. 3). - -Silicified Cretaceous fossils have been recovered from the Edwards -limestone of central Texas. The silicified fauna is restricted to a few -scattered localities, each of which may yield many unusually -well-preserved fossils. - - Replacement by iron compounds - -Several different iron compounds have been known to replace organic -matter. Many Texas limestones contain fossil snails and clams which have -had their original shell material replaced by iron compounds such as -limonite, hematite, marcasite, or pyrite. Certain of the fossiliferous -Tertiary sandstones of the Texas Gulf Coast area contain large amounts -of glauconite which commonly replaced organic material. - -In some areas entire faunas have been replaced by iron compounds. Such -is the case in the famous “Pyrite Fossil Zone” of the Pawpaw formation -(Lower Cretaceous) in Tarrant County. The fossils in this part of the -formation are very small or “dwarfed” and have been replaced by -limonite, hematite, or pyrite. Ammonites, clams, snails, and corals are -particularly abundant at this locality. - - - - - TRACES OF ORGANISMS - - -Fossils consist not only of plant and animal remains but of any evidence -of their existence. In this type of fossilization there is no direct -evidence of the original organism, rather there is some definite -indication of the former presence of some ancient plant or animal. -Objects of this sort normally furnish considerable information as to the -identity or characteristics of the organism responsible for them. - - - Molds and Casts - -Many shells, bones, leaves, and other forms of organic matter are -preserved as molds and casts. If a shell had been pressed down into the -ocean bottom before the sediment had hardened into rock, it may have -left the impression of the exterior of the shell. This impression is -known as a _mold_ (Pl. 2). If at some later time this mold was filled -with another material, this produced a _cast_. This cast will show the -original external characteristics of the shell. Such objects are called -_external molds_ if they show the external features of the hard parts -(Pl. 2, fig. 2) and _internal molds_ (Pl. 2, fig. 3) if the nature of -the inner parts is shown. - -Molds and casts are to be found in almost all of the fossil-bearing -rocks of Texas, and they make up a large part of most fossil -collections. It is particularly common to find fossil clams and snails -preserved by this method. This is primarily because their shells are -composed of minerals that are relatively easy to dissolve, and the -original shell material is often destroyed. - - [Illustration: PLATE 3 - Silicified Brachiopods - -All specimens from Permian limestones of the Glass Mountains, Brewster -County, Texas] - - Figures— - 1, 2. _Avonia_ sp., ×2. Ventral and side view of two pedicle valves - showing long slender spines. - 3. _Avonia_ sp., ×6. Young specimen showing attachment ring at apex. - 4-6. _Muirwoodia multistriatus_ Meek, ×4. Respectively, side and - ventral view of pedicle valve and dorsal view of brachial - valve. - 7-9. _“Marginifera” opima_ Girty. Respectively, ventral and side - view of pedicle valve showing long stout spines (×4) and - interior of brachial valve showing muscle scars and brachial - ridges (×2). - 10-13. _Aulosteges tuberculatus_ R. E. King, ×4. Respectively, side - and interior view of brachial valve showing muscle scars; - ventral view of pedicle valve showing brush of attachment - spines on ears; and ventral view of a young pedicle valve. - 14. _Avonia_ sp., ×4. Ventral view of a specimen with long spines. - 15, 16. _Avonia subhorrida_ (Meek), ×2. Ventral view of a pedicle - valve and dorsal view of a brachial valve showing spines on - both. - 17. _Avonia signata_ (Girty), ×2. Dorsal view of a large specimen - showing hairlike spines on brachial valve. - 18-20. _Prorichthofenia permiana_ (Shumard). Respectively, side and - posterior view of pedicle valve (×4) and interior of dorsal - valve (×2) showing anchor spines and interior spines of the - brachial valve. - 21. _Heteralosia hystricula_ (Girty), ×2. Cluster of individuals - attached to a large _Marginifera_. - Photograph courtesy of Dr. G. A. Cooper, U. S. National Museum. - - - Tracks, Trails, and Burrows - -Many animals have left records of their movements over dry land or the -sea bottom. Some of these, such as footprints (Pl. 4), indicate not only -the type of animal that left them but often provide valuable information -about the animal’s environment. - -Thus, the study of a series of dinosaur tracks would not only indicate -the size and shape of the foot but also provide some information as to -the weight and length of the animal. In addition, the type of rock -containing the track would help determine the conditions under which the -dinosaur lived. - -Some of the world’s most famous dinosaur tracks are to be found in the -Lower Cretaceous limestones in Somervell County, Texas. These -footprints, which are about 110,000,000 years old (Pl. 4), were -discovered in the bed of Paluxy Creek near the town of Glen Rose. Large -segments of the rock containing these tracks were collected by -paleontologists of the American Museum of Natural History in New York -City and the Texas Memorial Museum at Austin. Great slabs of limestone -were transported to the museums, replaced in their original position, -and are now on display as mute evidence of the gigantic size of these -tremendous reptiles. - -Invertebrates also leave tracks and trails of their activities, and -these markings may be seen on the surfaces of many sandstone and -limestone deposits. These may be simple tracks, left as the animal moved -over the surface, or the burrows of crabs or other burrowing animals. -Markings of this sort provide some evidence of the manner of locomotion -of these organisms and of the type of environment that they inhabited. - - - Coprolites - -Coprolites are fossil dung or body waste (fig. 1). These objects can -provide valuable information as to the food habits or anatomical -structure of the animal that made them. - - [Illustration: Fig. 1. Sketch of a coprolite—fossilized animal - excrement.] - - - Gastroliths - -These highly polished well-rounded stones (fig. 2) are believed to have -been used in the stomachs of reptiles for grinding the food into smaller -pieces. Large numbers of these “stomach stones” have been found with the -remains of certain types of dinosaurs. - - [Illustration: Fig. 2. Sketch of a gastrolith—the gizzard stone of an - ancient reptile.] - - - - - PSEUDOFOSSILS - - -Among the many inorganic objects formed by nature there are some that -bear superficial resemblance to plants or animals. Because they are -often mistaken for organic remains, these objects have been called -_pseudofossils_, or “false fossils.” - - - Dendrites - -[Illustration: Fig. 3. Dendrites. These thin branching mineral deposits - bear a marked resemblance to plants, hence they are called - pseudofossils.] - -Although these closely resemble the remains of ferns or other plant -material (fig. 3), dendrites are actually thin incrustations of -manganese dioxide. They are often found along the bedding planes of -Cretaceous and Paleozoic (geologic time scale, Pl. 1) limestones in many -parts of Texas. - - [Illustration: Plate 4 - Dinosaur tracks in limestone in bed of Paluxy Creek near Glen Rose, - Somervell County, Texas. - Photograph courtesy of the American Museum of Natural History. - Permission to reproduce by R. T. Bird.] - - - Slickensides - -These are striations that are produced when rock surfaces move past each -other while being fractured. Slickensides may superficially resemble -certain of the Pennsylvanian coal plants of Texas. - -Since slickensides are commonly at an angle to the bedding plane and -plant remains lie parallel to the bedding plane, the two are usually -easily distinguished. - - - Concretions - -Many shales and sandstones contain hardened masses of minerals and rock -that are often mistaken for fossils. These masses, called concretions, -are usually found weathered out of the surrounding rock and may assume -the shape of bones, flowers, vegetables, turtles, etc. Although these -concretions do not represent organic remains, it is sometimes possible -to find true fossils inside them. - - - - - WHERE AND HOW TO COLLECT FOSSILS - - -In fossil collecting, as in most “collecting” hobbies, the key to -success lies in knowing where to look, what equipment to use, and the -most effective methods of collecting. - - - - - COLLECTING EQUIPMENT - - -Fossil collecting is a relatively inexpensive hobby because it requires -a minimum of supplies and equipment. However, as in almost any hobby, -there are certain basic items of equipment that must be acquired. - - - Hammer - -The hammer is the basic tool in the collector’s kit. Almost any type of -hammer is satisfactory, but as collecting experience is gained it may be -desirable to get a geologist’s hammer. These hammers, also called -mineralogist’s or prospector’s picks, are of two types. One type has a -square head on one end and a pick on the other (Pl. 5): the other type -is similar to a stonemason’s or bricklayer’s hammer and has a chisel end -instead of the pointed pick end. The square head of the hammer is useful -in breaking or chipping harder rocks, and the chisel or pick end is good -for digging, prying, and splitting soft rocks. - - - Collecting Bag - -It will be necessary to have some type of bag in which to carry -equipment, fossils, and other supplies. A Boy Scout knapsack, musette -bag (Pl. 5), hunting bag, or similar canvas or leather bag is suitable. - - - Chisels - -A pair of chisels is useful when fossils must be chipped out of the -surrounding rock. Two sizes, preferably ½ and 1 inch, will usually -suffice. A small sharp punch or awl is effective in removing smaller -specimens from the softer rocks. - - - Wrapping Materials - -Some specimens are more fragile than others, and these should be handled -with special care. Several sheets of newspaper should always be kept in -the collecting bag, and each specimen should be wrapped individually as -it is collected. Such precautions taken in the field will usually -prevent prized specimens from being broken or otherwise damaged. In -addition to newspaper, it is wise to carry a supply of tissue paper in -which to wrap more fragile specimens. - - - Map, Notebook, and Pencil - -It is most important to have some method of recording where the fossils -were found. It is very easy to forget where the material was collected, -and one should _never_ rely on memory. A small pocket-sized notebook is -inexpensive and just the right size to carry in the field. - -A highway or county map should be used to find the geographic location -of each collecting locality. Maps of Texas counties can be obtained from -the Texas Highway Department, File D-10, Austin 14, Texas. These maps -come in three different sizes, but for most purposes the 18×25-inch -sheets, with a scale of ½ inch = 1 mile, will be satisfactory. These are -available for all counties and may be purchased at a nominal price. - - - Magnifying Glass - -A magnifying glass or hand lens (Pl. 5) is useful for looking at small -specimens and will also prove helpful in examining the finer details of -larger fossils. A 10-power magnification is satisfactory for most -purposes, and several inexpensive models are available. - - - Paper or Cloth Bags - -Small bags are useful in separating specimens from different localities. -Heavy-duty hardware bags for large rough material and medium-weight -grocery bags for smaller specimens may be used. Locality data may be -written directly on the bag or on a label placed inside with the -fossils. As an added precaution some collectors do both. The more -serious collector may want to use a cloth geological sample bag (Pl. 5). - - [Illustration: Plate 5 - FOSSIL COLLECTING EQUIPMENT] - - GEOLOGIC HAMMER (Chisel end) - MAGNIFYING GLASS - GEOLOGIC HAMMER (Pick end) - COLLECTING BAG - SAMPLE SACK - - - Other Useful Items - -The items described above are those that are most needed and constitute -the basic equipment of the fossil hunter. The serious amateur may wish -to include certain additional items which will place his collecting on a -more professional basis. Some of these accessory items are: - -1. A _topographic map_ of the collecting area. These are available for -many parts of the State and are published and distributed at nominal -cost by the United States Geological Survey, Washington, D. C., and/or -Denver, Colorado. The Survey can supply an index sheet showing all such -maps available for Texas. - -2. A _geologic map_ of the collecting area if one is available. The list -of publications of the Bureau of Economic Geology should be consulted to -see if a geologic report or map of the area has been published. This -list may be obtained without charge from the Bureau of Economic Geology, -The University of Texas, Austin 12, Texas. - -3. The _geologic map of Texas_. Although a geologic map of Texas is -included in this publication (Pl. 10), the scale is so small that its -use is somewhat limited. For more detailed work a larger geologic map in -color (scale: 1 inch = 31.56 miles) may be ordered from the Bureau. The -sale price is 25 cents. - -4. A _compass_ for more accurate location of collecting localities. - -5. _Adhesive_ or _masking tape_. The locality information can be written -on the tape and applied directly to the specimen. - -6. _Paper labels_ (about 3×5 inches). A properly completed label should -be placed inside each bag of material. - - - - - WHERE TO LOOK - - -Knowing where to look for fossils is a very important part of fossil -collecting. It has already been pointed out that igneous and metamorphic -rocks are not likely to be fossiliferous, but that most fossils are -found in marine sedimentary rocks. These sediments were deposited under -conditions that were favorable for organisms during life and which -facilitated preservation after death. Limestones, limy shales, and -certain types of sandstones are typically deposited under such -conditions. - -One should look particularly for areas where rocks formed from marine -sediments lie relatively flat and have not been greatly disturbed by -heat, pressure, and other physical or chemical changes. If the rocks -appear to have undergone considerable folding and fracturing, there is -great likelihood that any fossils that were present have been destroyed -or damaged by this action. - -Quarries are good places to look but one should be sure to obtain -permission before entering. Rock exposures in quarries are rather fresh -but have undergone some weathering. Quarries have been opened in many of -the limestone formations of Texas, and large numbers of fine specimens -have been collected in some of these excavations. Certain Lower -Cretaceous limestones are useful for road metal, building stone, or in -the manufacture of portland cement, and extensive quarrying has been -undertaken in the Edwards Plateau region of Texas (Pl. 9). Bones and -petrified wood are frequently found in sand and gravel quarries in many -parts of the State. - -Particular attention should be given to all railroad and highway cuts as -rocks exposed in this way are usually still in their original position -and are fairly well weathered. Cuts made by recent construction are -usually more productive after they have undergone a period of weathering -as this helps to separate the fossils from their enclosing rocks. - -Gullies, canyons, and stream beds are also good places to examine. These -areas are continually subjected to the processes of erosion or stream -action, and new material is uncovered year after year. - -If there are abandoned coal mines nearby, the dumps of waste rock around -the mine shafts could be checked. A careful examination of such waste -may reveal fine specimens of well-preserved plant fossils. - -Coal has been mined in several parts of Texas, and abandoned shafts or -dumps are still present in some counties. The bituminous coals of Texas -are predominantly Pennsylvanian in age, and mining has been carried on -in the following counties: Eastland, Erath, Jack, Palo Pinto, Parker, -Wise, Young. - - - - - HOW TO COLLECT - - -When a likely collecting spot has been located, the ground should be -examined very carefully to see if there are any rock fragments which -contain pieces of shell or the imprints of leaves or other organisms. - -If the fossils have been freed by weathering, they can be easily picked -up and placed in the bag. Many times, however, it will be necessary to -take the hammer and very carefully remove the surrounding rock. Smaller -specimens may be more safely freed with the careful use of the proper -size chisel by gently tapping the chisel and gradually chipping away the -_matrix_—the rock that is holding the specimen. After most of the matrix -has been removed, the fossil should be carefully wrapped and placed in -the collecting bag. - -Before leaving a collecting locality, one should be sure to record its -geographic location and the geologic age of the rock in which the -fossils were found. The place should be located on the map and the -locality entered in the notebook in such a manner that it could easily -be located again for additional collecting. If a county or topographic -map is available, it is wise to mark the locality on the map. The -geographic and geologic data should be written on a label placed in the -bag of fossils collected at that particular locality. In addition, many -collectors find it helpful to write the locality on the outside of each -bag of fossils. - -Material from separate localities should be kept in individual cloth or -paper bags, and the collector should take every precaution to keep the -labels with their respective fossils. Remember that _a fossil without a -locality is hardly worth the paper it is wrapped in_. - -The collector should _always_ ask the land owner’s permission before -entering or collecting on private property. One should respect all -property, especially livestock and fences, and leave the area cleaner -than when entered. If these precautions are observed, future collectors -will probably be welcome to return for additional collecting. - - - - - CLEANING AND PREPARATION OF FOSSILS - - -It is usually necessary to do the final cleaning and preparation of -fossils at home or in the laboratory, for most fossils brought in from -the field require considerable preparation before they are ready for -display. - -Excess matrix should be carefully removed with hammer and chisel; blows -should always be directed away from the fossil. Smaller tools (needles, -tweezers, and awls) should be used in the final preparation stage, and -one should work carefully to avoid damaging the specimen. Before -starting the final cleaning, it will be helpful to place the fossils in -water and let them soak overnight. This will loosen much of the excess -rock, and most of the softer material can then be removed with a small -scrub brush or tooth brush. Mounted needles can be used to clean more -delicate specimens or around the smaller structures of larger fossils. -It may be advisable to use the magnifying glass when working with small -fossils or with delicate surface structures of larger specimens. - -Broken fossils can be repaired with clear plastic household cement, and -specimens that are crumbling may be coated with pure white shellac, -thinned collodion, or clear nail polish. The latter is preferred as it -is not as likely to crack. Fragments of bone are particularly apt to -crumble upon exposure to the air. This type of fossil is normally quite -fragile and should be excavated with great care and shellaced as soon as -dry. - -Dilute hydrochloric acid may be used in removing silicified fossils from -a calcareous matrix. The material to be etched should be placed in a -pottery or glass container and covered with water. Acid should then be -added to the water very slowly and until large numbers of bubbles are -given off. Each time the bubbling ceases, more acid should be added and -this process should be repeated until the fossil is free of matrix. This -procedure should be carried on in a well-ventilated place, and the acid -should be handled with extreme caution. Hydrochloric acid can cause -damage or serious injury and the fumes are extremely corrosive. - - - - - HOW FOSSILS ARE NAMED - - -In order to get the maximum pleasure out of fossil collecting, most -amateur paleontologists want to identify and classify the fossils that -they have collected. This requires some knowledge of how fossils are -classified and how they receive their scientific names. - - - - - THE SCIENCE OF CLASSIFICATION - - -The number of organisms, both living and extinct, is so great that some -system of classification is needed to link them all together. Many -fossils bear distinct similarities to plants and animals that are living -today, and for this reason paleontological classification is similar to -that used to classify modern organisms. This system, known as the system -of _binomial nomenclature_, was first used consistently in 1758 by Linné -(or Linnaeus), an early Swedish naturalist. - -Scientific names established in accordance with the principles of -binomial nomenclature consist of two parts: the _generic_ (or _genus_) -name and the _trivial_ name. These names are commonly derived from Greek -or Latin words which are usually descriptive of the organism or fossil -being named. They may, however, be derived from the names of people or -places, and in such instances the names are always Latinized. Greek or -Latin is used because they are “dead” languages and not subject to -change. They are also “international” languages in that scientists all -over the world can use the same names regardless of what language they -write in. The system of binomial nomenclature has led to the development -of the science of _taxonomy_, the systematic classification and naming -of plants and animals according to their relationships. - - - - - THE UNITS OF CLASSIFICATION - - -The world of organic life has been divided into the plant and animal -kingdoms. These kingdoms have been further divided into larger divisions -called _phyla_ (from the Greek word _phylon_, a race). Each phylum is -composed of organisms with certain characteristics in common. For -example, all animals with a spinal cord (or notochord) are assigned to -the phylum Chordata. - -The phylum is reduced to smaller divisions called _classes_, classes are -divided into _orders_, orders into _families_, families into _genera_, -and each genus is divided into still smaller units called _species_. A -species may be further reduced to subspecies, varieties, or other -subspecific categories, but these need not concern us in a publication -of this nature. - -The following table illustrates the use of binomial nomenclature in the -classification of man, a clam, and a dog. - - Unit Man Dog Clam - Kingdom Animalia Animalia Animalia - Phylum Chordata Chordata Mollusca - Class Mammalia Mammalia Pelecypoda - Order Primates Carnivora Eulamellibranchia - Family Hominidae Canidae Veneridae - Genus _Homo_ _Canis_ _Venus_ - Species _sapiens_ _familiaris_ _mercenaria_ - -The generic name and the trivial name constitute the _scientific name_ -of a species and according to this system of classification the -scientific name of all living men is _Homo sapiens_. It is obvious that -there are many variations among individual men, but all men have certain -general characteristics in common and are therefore placed in the same -species. - -In a scientific name, the generic name is always started with a capital -letter and the trivial name with a small letter. Both names must be -italicized or underlined. - -The name of the author (the person who first described the fossil) -usually appears following the scientific name. The date of the -scientific publication containing the original description of the fossil -is often placed after the author. For example: - - _Turrilites worthensis_ Adkins and Winton 1920 - -With the large numbers of plants and animals that are living today, plus -those of the past, random naming would result in much confusion. For -this reason scientists have established strict rules that must be -followed when a specimen is named. The strict application of these rules -enables scientists in all parts of the world to assign scientific names -without fear of duplication. - - - - - IDENTIFICATION OF FOSSILS - - -The beginning collector is usually content to know if his specimen is a -clam or a snail or a fern or a palm leaf. But as the collection grows, -it becomes increasingly desirable to know the scientific name of each -fossil. - -When he starts to identify fossils it may be helpful to show them to a -geology teacher if a college or university is nearby. Most teachers are -glad to be of help and will probably have similar specimens in their own -collections. As all colleges do not have geology departments, a list of -institutions with geologists on their faculties is included at the end -of this section of the handbook (p. 27). In addition, many of the -science teachers in the public schools are familiar with fossils and can -give helpful suggestions as to how to classify material. - -Museums are also good places from which to get help. If the museum has a -geological collection, it will be most helpful to compare specimens with -the fossils in their collections and to ask the museum personnel for -advice. In addition to the above sources of information, local -professional geologists are usually familiar with the geology of the -local area and the paleontological literature of the region. - -Possibly local librarians can recommend books, encyclopedias, or other -publications that will be of help. Members of a local rock and mineral -club, if one is available, are another source of information. Many times -these collectors can pass along good ideas and tell exactly which books -to consult. - -After books or journals describing the fossils of the area have been -located, the collected specimens should be closely compared with any -illustrations that are shown. Each fossil should be examined carefully, -its more characteristic features noted, and it should again be compared -with the illustrations and descriptions in the book. The phylum or class -to which the specimen belongs should be determined first. For example, -the genus and species of a certain fossil may not be known, but it looks -like a snail and accordingly it is named a gastropod (for class -Gastropoda, the snail class), and this is, at least, a start in -determining the scientific name of that particular fossil. The -descriptive material in the text of each reference will usually point -out the more detailed features which will be diagnostic of the genus or -species. - -The illustrations and descriptive material in this publication will also -be of considerable help in identification. Many illustrations of the -more common invertebrate fossils have been included, but the publication -was not designed primarily for use in fossil identification. Rather, it -is intended to guide the amateur or student who is interested in fossil -collecting, and to furnish suggestions as to how collecting may be more -effectively pursued. - - - - - USE OF IDENTIFICATION KEYS - - -Fossil identification keys may be useful in helping the beginning -collector identify specimens. The collector compares a fossil with the -key description and eliminates those characters that do not fit the -specimen. - -The key used in this handbook is based primarily on _symmetry_—the -orderly arrangement of the parts of an object with reference to lines, -planes, or points. The shape of the shell or body, presence or absence -of coiling, and presence or absence of body partitions are also useful -criteria in identifying fossils. To use the key the beginner should know -something about symmetry. Two major types of symmetry are used in this -key. - - 1. _Radial symmetry_—the symmetrical repetition of parts around an - axis. This is the symmetry of a wheel, and any vertical section - through the center of the object divides it into symmetrical halves - (fig. 4a). - - 2. _Bilateral symmetry_—the symmetrical duplication of parts on each - side of a plane (fig. 5). The plane divides the object into two halves - that are mirror images of each other. This is the symmetry of a plank. - -It should be noted that many objects may have both kinds of symmetry. -For example: A cone when viewed from the top has radial symmetry and -when viewed from the side shows bilateral symmetry (fig. 4a, b). - - [Illustration: Fig. 4. Types of symmetry in a fossil coral. (a) Radial - symmetry. (b) Bilateral symmetry.] - - [Illustration: Fig. 5. Bilateral symmetry as displayed by a typical - fossil brachiopod.] - -An illustration of the use of the key on pages 26-27 follows. Assuming -that a specimen displays radial symmetry, this means that it belongs -under Part I on the key. If the fossil has a tapering, cylindrical, -cone-shaped shell (“A” on the key), the subheadings under the “A” part -of the key are examined. Should the specimen have a shell which is -round, tapering at one end, with transverse septa or sutures (number 2 -under “A”), it is probably a cephalopod. This is indicated on the right -hand side of the page. Number 1 under “A” is eliminated because the -fossil did not have longitudinal radial partitions within the shell. - -Some fossils display no apparent symmetry and such a fossil would be -referred to Part III of the key. If this fossil had internal transverse -partitions “A” would be eliminated. If the fossil was not a coiled -fossil “B” would also be eliminated and we would proceed directly to -“C”—uncoiled fossils. If the specimen is a branching twig-like fossil, -numbers 1, 2, and 3 would be eliminated and the specimen referred to -number 4 (Branching twig-like fossils). Should the specimen have evenly -distributed relatively large openings with radial longitudinal -partitions or septa, the specimen is probably a colonial coral (“b” -under number 4 on the key). The “a” part of number 4 would be eliminated -because the coral had large openings and radial longitudinal septa. - -Once a tentative identification has been made from the key, pictures and -descriptions of this fossil group are examined to establish a more -precise identification. It should be remembered that keys are not -perfect, and the collector should not expect to be able to identify -every specimen with this key. - - - - - IDENTIFICATION KEY TO MAIN TYPES OF INVERTEBRATE FOSSILS - - -(Instructions on pages 23-25 for use of key) - - I. Fossils displaying radial symmetry—symmetrical repetition of parts - around a central axis - A. Fossil tapering, cylindrical, cone-shaped: - 1. Fossil with longitudinal radial partitions or septa; - cone-shaped - Coral - 2. Shell with transverse septa or sutures; tapering at one end - Cephalopod - 3. Shell without internal septa or partitions: - a. Shell large, heavy; usually with external longitudinal ribs. - Occur only in Cretaceous rocks - Rudistid - b. Shell small (usually less than 2 inches long), tusk-shaped, - open at both ends. Rare in Paleozoic and Mesozoic rocks - Scaphopod - B. Fossil disk-shaped or flattened dome-shaped: - 1. Fossil with radiating star pattern on top - Echinoid - 2. Fossil subconical to hemispherical, dome-shaped; base concave - or flat; minute pits or pores covering surface; typically - small (less than 3 inches across) - Bryozoa - 3. Fossil small (less than ½ inch); generally disk-shaped - Foraminifera (orbitoidid) - 4. Fossil disk-shaped or button-like; with longitudinal, radial - partitions or septa - Coral - C. Fossil composed of segments or plates: - 1. Fossil composed of circular segments, disks, or chambers; when - united form cylinder: - a. Tapered shell - Cephalopod - b. Non-tapered, segments small and of relatively uniform - thickness with hole in center; individual columnals - disk-shaped - Crinoid stem - 2. Fossil composed of many-sided plates: - a. Bud-shaped fossil of 13 wedge-shaped plates - Blastoid - b. Cup-shaped fossil of many curved plates surrounded by - branching arms - Crinoid - II. Fossils displaying bilateral symmetry—symmetrical duplication of - parts on each side of a plane - A. Fossil coiled in a single plane: - 1. Shell divided by internal transverse partitions or sutures - Cephalopod - 2. Shell without internal partitions or sutures - Gastropod - 3. Shell small; spindle-shaped; resembles wheat grain. Common in - Pennsylvanian and Permian rocks - Foraminifera (fusulinids) - B. Fossil not coiled: - 1. Shells or valves similar to clams: - a. Plane of symmetry parallel to hinge; equivalved - Pelecypod - b. Plane of symmetry (almost bilaterally symmetrical) at right - angles to hinge line; mostly inequivalved; strongly ribbed. - “Scallop-like” with “ears.” Rare in Paleozoic rocks - Pelecypod - c. Plane of symmetry at right angles to hinge line; - inequivalved; not “scallop-like” and without “ears.” Larger - valve commonly has an opening in beak. Common in Paleozoic - rocks - Brachiopod - 2. Fossil tapering, cylindrical, cone-shaped: - a. Fossil with internal longitudinal, radial septa or - partitions; cone-shaped - Coral - b. Shell with internal transverse partitions or sutures; - tapering at one end - Cephalopod - c. Shell without internal septa or partitions. - (1) Shell large, heavy; usually with external longitudinal - ribs. Occur only in Cretaceous rocks - Rudistid - (2) Shell small (usually less than 2 inches), tusk-shaped, - open at both ends. Rare in Paleozoic and Mesozoic rocks - Scaphopod - 3. Fossil heart-shaped, domed or flattened; radial star pattern on - top - Echinoid - 4. Fossil segmented: - a. Fossil divided into 3 lobes; may be curled up. Not found in - Mesozoic or Cenozoic rocks - Trilobite - b. Fossil flattened or elongate; resembles shrimp, crab, or - crayfish - Crustacean - III. Fossils displaying no apparent symmetry - A. Shell without transverse internal partitions or sutures: - 1. Shell coiled like ram’s horn, low spired, opening of shell very - large; surface has concentric ridges. Shell has two valves; - smaller, flattened valve not often found. In Texas found only - in Cretaceous rocks - Pelecypod - (Note: Some Paleozoic gastropods, “2,” closely resemble larger - valve of these pelecypods) - 2. Shell tightly coiled; most have higher spire than “1.” Opening - of shell smaller than “1”; shell not as rough as “1” and has - only one valve - Gastropod - B. Coiled fossils; coiling not in one plane: - 1. Shell with transverse internal partitions or sutures: - a. Partitions always smooth; thick shelled; loosely and - irregularly coiled, usually in large compact masses of many - individual shells. Occur only in Cretaceous rocks - Caprinid - b. Partitions (sutures) usually wrinkled; relatively thin - shelled; mostly regularly and tightly coiled; occur as - separate individual specimens - Cephalopod - 2. Shell without transverse internal partitions or sutures - Gastropod - 3. Solid spiral ridge around central axis; resembles a corkscrew - Bryozoa - C. Uncoiled fossils: - 1. Fossil resembles a narrow saw blade; typically found as thin - film of carbon. Not found in Mesozoic or Cenozoic rocks - Graptolite - 2. Fossil irregularly cone-shaped; longitudinal radial partitions - or septa - Coral - 3. Shell resembles a clam or oyster shell but valve or shell not - symmetrical - Pelecypod (mostly oysters) - 4. Branching twig-like fossils: - a. Fossils covered with minute pores or openings - Bryozoa - b. Fossils with evenly distributed, relatively large openings - with longitudinal radial partitions or septa - Colonial coral - 5. Lace-like fossils; occur as thin sheets or films - Bryozoa - 6. Fossils composed of radiating masses of polygonal or circular - tubes containing radial septa - Colonial coral - 7. Irregular fossils; typically cylindrical with rough surface: - a. Fossil has large axial opening and thick wall; usually has - external longitudinal ribs. Occurs only in Cretaceous rocks - Rudistid - b. Fossil solid with no large axial opening; surface with small - pits or pores (fewer than in Bryozoa). In Texas, occurs most - commonly in Pennsylvanian and Permian rocks - Sponge - - - - - LIST OF TEXAS COLLEGES OFFERING GEOLOGY COURSES - - - A.&M. College of Texas, College Station - Amarillo College, Amarillo - Arlington State College, Arlington - Austin College, Sherman - Baylor University, Waco - Blinn College, Brenham - Corpus Christi, University of, Corpus Christi - Del Mar College, Corpus Christi - East Texas State College, Commerce - Hardin-Simmons University, Abilene - Henderson County Junior College, Athens - Houston, University of, Houston - Howard County Junior College, Big Spring - Kilgore College, Kilgore - Lamar State College of Technology, Beaumont - Lee College, Baytown - McMurry College, Abilene - Midwestern University, Wichita Falls - North Texas State College, Denton - Odessa College, Odessa - Pan American College, Edinburg - Rice University, Houston - St. Mary’s University, San Antonio - San Angelo College, San Angelo - San Antonio College, San Antonio - Southern Methodist University, Dallas - South Texas College, Houston - Southwestern University, Georgetown - Stephen F. Austin State College, Nacogdoches - Sul Ross State College, Alpine - Tarleton State College, Stephenville - Texarkana College, Texarkana - Texas Christian University, Fort Worth - Texas College, Tyler - Texas College of Arts and Industries, Kingsville - Texas Technological College, Lubbock - Texas Western College, El Paso - The University of Texas, Austin - Trinity University, San Antonio - Tyler Junior College, Tyler - West Texas State College, Canyon - - [Illustration: Plate 6 - Fossil Identification Chart - I RADIAL SYMMETRY] - - A. Tapering, cylindrical cone-shaped fossils - 1. Cone-shaped with longitudinal partitions or septa - Coral - 2. Fossils with septa or sutures; tapering at one end - Cephalopod - 3. Shell without internal partitions or sutures - a. Shell large heavy, external longitudinal ribs. Cretaceous only - Rudistid - b. Shell small, tusk-shaped open at both ends. Rare in Paleozoic - and Mesozoic - Scaphopod - B. Disc or dome-shaped fossils - 1. Star pattern on top - Echinoid - 2. Subconical small pits or pores on top - Bryozoan - 3. Small disc-shaped (less than ½ inch) - Orbitoid Foraminifera - 4. Disc-shaped or button-like, with longitudinal partitions or septa - Coral - C. Fossils composed of segments or plates - 1. Circular discs or chambers; when united form cylinder - a. Tapered shell - Cephalopod - b. Not tapered, segments small of uniform thickness, hole in - center - Crinoid Stem - 2. Fossil composed of many-sided plates - a. Bud-shaped, 13 wedge-shaped plates - Blastoid - b. Cup-shaped, many curved plates branching arms - Crinoid - - [Illustration: Plate 7 - Fossil Identification Chart - II BILATERAL SYMMETRY] - - A. Fossil coiled in a single plane - 1. Shell divided by internal transverse partitions or sutures - Cephalopod - 2. Shell without internal partitions or sutures - Gastropod - 3. Shell small, spindle-shaped; resembles wheat grain. Pennsylvanian - and Permian - Foraminifera fusulinid - B. Fossil not coiled - 1. Shells or valves similar to clams - a. Plane of symmetry parallel to hinge; equivalved - Pelecypod - b. Plane of symmetry almost at right angles to hinge; strongly - ribbed; “Scallop-like” with “ears”, inequivalved - Pelecypod - c. Plane of symmetry at right angles to hinge-line; without - “ears”, not “Scallop-like”; commonly with opening in beak, - inequivalved - Brachiopod - 2. Fossil tapering, cylindrical or cone-shaped - a. Cone-shaped, internal longitudinal partitions or septa - Coral - b. Tapered, internal transverse partitions - Cephalopod - c. Shell without internal septa or partitions - (1.) Shell large heavy, longitudinal ribs. Cretaceous only - Rudistid - (2.) Shell small, tusk-shaped, open at both ends, rare in - Paleozoic and Mesozoic rocks - Scaphopod - 3. Fossil heart-shaped, domed or flattened; star pattern on top - Echinoid - 4. Fossil segmented - a. Divided into 3 lobes, may be curled up. Paleozoic only - Trilobite - b. Flattened or elongate, resembles shrimp - Crustacean - - [Illustration: Plate 8 - Fossil Identification Chart - III NO APPARENT SYMMETRY] - - A. Shell without transverse partitions or sutures - 1. Shell coiled like ram’s horn, low spired; shell has two valves, - smaller flattened valve often missing. In Texas exclusively - Cretaceous - Pelecypod - 2. Shell tightly coiled, most have higher spire than 1, shell - smaller and not as rough as 1, has only one valve - Gastropod - B. Coiled fossils, coiling not in one plane - 1. Shell with transverse internal partitions or sutures - a. Partitions always smooth, thick shelled, loosely and - irregularly coiled, in Texas exclusively Cretaceous - Caprinid - b. Partitions (sutures) generally wrinkled, regularly and tightly - coiled - Cephalopod - 2. Shell without transverse internal partitions or sutures - Gastropod - 3. Solid spiral ridge around central axis, resembles corkscrew - Bryozoan - C. Uncoiled fossils - 1. Fossil resembles narrow saw blade. Paleozoic only - Graptolite - 2. Fossil irregularly cone-shaped, longitudinal partitions or septa - Coral - 3. Shell resembles clam or oyster, nonsymmetrical - Pelecypod (mostly oysters) - 4. Branching twig-like fossils - a. Covered with minute pores or openings - Bryozoa - b. With evenly distributed larger openings with septa - Colonial coral - 5. Lace-like fossils, occur as thin sheets or films - Bryozoa - 6. Masses of circular or polygonal tubes with septa - Colonial coral - 7. Irregular fossils, cylindrical with rough surface - a. Large axial opening with thick wall, external longitudinal - ribs. Cretaceous only - Rudistid - b. Solid, no opening, small pits or pores. Pennsylvanian or - Permian - Sponge - - - - - CATALOGING THE COLLECTION - - -After the fossils have been cleaned and tentatively identified, they -should be cataloged. This is necessary to enable the collector to have a -record of his collection and to furnish as much information as possible -about each individual fossil. - -The collecting data can be taken from the labels that were placed in -each bag of fossils as they were collected, or from the field notebook. -Actually, it is wise to check one against the other. This information -should then be entered in some type of record book and also placed on a -more permanent label which is put in the tray or box with the fossil. -The catalog and label should contain such pertinent data as (1) the -scientific name of the fossil, (2) the geologic formation from which the -specimen was collected, (3) the exact geographic location of the -collecting locality, (4) the name of the collector, (5) the date the -fossil was collected, and (6) the catalog number of the specimen. The -latter is usually placed in the upper right hand corner of the label -(fig. 6) and corresponds with a like number in the record book. - - - - - Specimen No. P-185 - NAME Spirifer rockymontanus - FORMATION Big Saline (Penn.) - LOCALITY Little Brady Creek, McCulloch Co., Tex. - (1000′ NE of Smith ranch House) - COLLECTOR F. B. Plummer - DATE July 1937 - - [Illustration: Fig. 6. A brachiopod showing the catalog number on it, - and the accompanying label that pertains to the specimen.] - -The entries in the catalog should be numbered consecutively, and all -specimens from the same locality should bear the same number. This -number should be written on the fossil with India ink, preferably on any -remaining matrix or on some inconspicuous part of the specimen (fig. 6). -If the surface of the fossil is too coarse or porous for ink, the -catalog number can be written on a small patch of white enamel or clear -nail polish painted on the specimen. After the ink has dried it should -be coated with a dab of clear shellac or clear nail polish to help -preserve the number. If each specimen is numbered, it can easily be -identified even if it should become separated from its label. - - - - - HOW FOSSILS ARE USED - - -Fossils are useful in a number of different ways, for each specimen -provides some information about when it lived, where it lived, and how -it lived. - -Fossils are very important, for example, in tracing the development of -the plants and animals of our earth. This is possible because the -fossils in the older rocks are usually primitive and relatively simple; -but a study of similar specimens that lived in later geologic time shows -that the fossils become progressively more complex and more advanced in -the younger rocks. - -Some fossils, for example, the reef-building corals, appear to have -always lived under much the same conditions as they live today. Hence, -it is reasonably certain that the rocks containing fossil reef corals -found in place (that is, where they were originally buried), were -deposited in warm, fairly shallow, salt water. By studying the -occurrence and distribution of such marine fossils, it is possible to -outline the location and extent of prehistoric seas. Moreover, the type -of fossils present will frequently give some indication as to the bottom -conditions, depth, temperature, and salinity of these ancient bodies of -water. - -Probably the most important use of fossils is for purposes of -_correlation_—the process of demonstrating that certain rock layers are -closely related to each other. By correlating or “matching” the beds -containing specific fossils, it is possible to determine the -distribution of geologic units of similar age. Some fossils have a very -limited vertical or geologic range and a wide horizontal or geographic -range. In other words, they lived but a relatively short period in -geologic time but were rather widely distributed during their relatively -short life. Such fossils are known as _index fossils_ or _guide fossils_ -and are especially useful in correlation because they are normally only -associated with rocks of one certain age. - - [Illustration: Fig. 7. Sketches of two types of micropaleontological - slides. (a) Multiple space faunal slide. (b) Single-hole slide.] - -Microfossils are often very valuable as guide fossils for the petroleum -geologist. The micropaleontologist washes the well cuttings from the -drill hole and separates the tiny fossils from the surrounding rocks. -The specimens are then mounted on special slides (fig. 7) and studied -under the microscope. Information derived from these fossils often -provides valuable data on the age of the subsurface formation and the -possibilities of oil production. Microfossils are particularly valuable -in the oil fields of the Gulf Coast region of Texas. In fact, some of -the oil-producing zones in this area have even been named for certain -key genera of microfossils. For example, the “het” zone of Oligocene age -(geologic time scale, Pl. 1) is named for the genus _Heterostegina_, -which is a tiny one-celled animal. Other microfossils, such as -fusulinids, ostracodes, spores, and pollens, are also used to identify -subsurface formations in many other parts of the State. - -Plant fossils are very useful as climatic indicators but are not too -reliable for purposes of age determination. They do, however, provide -much information about the development of plants throughout geologic -time. - - - - - GEOLOGIC HISTORY - - -The geologic history of our earth has been recorded primarily in marine -sedimentary rocks, and this record indicates that our earth is very old -and that life has been present for many millions of years. The earth is -not only extremely old (more than 3½ billion years of age), but it has -also undergone many changes which have taken place slowly but steadily -and have greatly affected both the earth and its inhabitants. The -earth’s physical features have not always been as they are seen today. -Geologic research has shown that mountains now occupy the sites of -ancient seas, and that coal is being mined where swamps existed millions -of years ago. Furthermore, there is much evidence to indicate that -plants and animals have also undergone great change. The trend of this -organic change is, in general, toward more complex and advanced forms of -life, but some forms have remained virtually unchanged and others have -become extinct. - -In order to interpret geologic history, the earth scientist must attempt -to gather evidence of the great changes in climate, geography, and life -that took place in the geologic past. The record of these changes can be -found in the rocks, and here is found the story of the various events in -earth history. - - - - - GEOLOGIC COLUMN AND TIME SCALE - - -In order to discuss fossils and the age of the rocks containing them, it -is necessary to become familiar with the _geologic column_ and the -_geologic time scale_ (Pl. 1). - -The _geologic column_ refers to the total succession of rocks, from the -oldest to most recent, that are found either locally or in the entire -earth. Thus, the geologic column of Texas includes all rock divisions -known to be present in this State. By referring to the geologic column -previously worked out for any given area, the geologist can determine -what type of rocks he might expect to find in that particular region. - -The _geologic time scale_ is composed of units which represent intervals -of geologic time, during which were deposited the rocks represented in -the geologic column. These time units are used by the geologist to date -the events that have taken place in the geologic past. - -The largest unit of geologic time is an era, and each era is divided -into smaller time units called _periods_. A period of geologic time is -divided into _epochs_, which, in turn, may be subdivided into still -smaller units. The geologic time scale might be roughly compared to the -calendar in which the year is divided into months, months into weeks, -and weeks into days. Unlike years, however, geologic time units are -arbitrary and of unequal duration, and the geologist cannot be positive -about the exact length of time involved in each unit. The time scale -does, however, provide a standard by which he can discuss the age of -fossils and their surrounding rocks. By referring to the time scale it -may be possible, for instance, to state that a certain event occurred -during the Paleozoic era in the same sense that one might say that -something happened during the American Revolution. - -There are five eras of geologic time, and each has been given a name -that is descriptive of the degree of life development that characterizes -that era. Hence, Paleozoic means “ancient-life,” and the era was so -named because of the relatively simple and ancient stage of life -development. - -The eras, a guide to their pronunciation, and the literal translation of -each name is shown below. - - Cenozoic (SEE-no-zo-ic)—“recent-life” - Mesozoic (MES-o-zo-ic)—“middle-life” - Paleozoic (PAY-lee-o-zo-ic)—“ancient-life” - Proterozoic (PRO-ter-o-zo-ic)—“primitive-life” - Archeozoic (AR-kee-o-zo-ic)—“beginning-life” - -Archeozoic and Proterozoic rocks are commonly grouped together and -referred to as Precambrian in age. The Precambrian rocks have been -greatly contorted and metamorphosed, and the record of this portion of -earth history is most difficult to interpret. Precambrian time -represents that portion of geologic time from the beginning of earth -history until the deposition of the earliest fossiliferous Cambrian -strata. If the earth is as old as is believed, Precambrian time may -represent as much as 85 percent of all geologic time. - -The _oldest_ era is at the _bottom_ of the list because this part of -geologic time transpired first and was then followed by the successively -younger eras which are placed above it. Therefore, the geologic time -scale is always read _from the bottom of the chart upward_. This is, of -course, the order in which the various portions of geologic time -occurred and during which the corresponding rocks were formed. - -As mentioned above, each of the eras has been divided into periods, and -most of these periods derive their names from the regions in which the -rocks of each were first studied. For example, the Pennsylvanian rocks -of North America were first studied in the State of Pennsylvania. - -The Paleozoic era has been divided into seven periods of geologic time. -With the oldest at the bottom of the list, these periods and the source -of their names are: - - Permian (PUR-me-un)—from the Province of Perm in Russia - Pennsylvanian (pen-sil-VAIN-yun)—from the State of Pennsylvania - Mississippian (miss-i-SIP-i-un)—from the Upper Mississippi Valley - Devonian (de-VO-ni-un)—from Devonshire, England - Silurian (si-LOO-ri-un)—for the Silures, an ancient tribe of Britain - Ordovician (or-doe-VISH-un)—for the Ordovices, an ancient tribe of - Britain - Cambrian (KAM-bri-un)—from the Latin word _Cambria_, meaning Wales - -The Carboniferous period in Europe includes the Mississippian and -Pennsylvanian periods of North America. Although this classification is -no longer used in the United States, the term Carboniferous will be -found in many of the earlier geological publications and on many of the -earlier geologic maps. - -The periods of the Mesozoic era and the source of their names are: - - Cretaceous (cre-TAY-shus)—from the Latin word _creta_, meaning chalky - Jurassic (joo-RAS-ik)—from the Jura Mountains of Europe - Triassic (try-ASS-ik)—from the Latin word _triad_, meaning three - -In Texas, the Cretaceous has two divisions, known as either Lower -Cretaceous and Upper Cretaceous or as Comanche series and Gulf series, -respectively. These designations are for rocks of nearly equivalent age, -and both sets of terms have been used by geologists and in publications. -In this handbook, both sets of terms are used interchangeably, that is, -Lower Cretaceous and/or Comanche series and Upper Cretaceous and/or Gulf -series. - -The Cenozoic periods derived their names from an old outdated system of -classification which divided all of the earth’s rocks into four groups. -The two divisions listed below are the only names of this system which -are still in use: - - Quaternary (kwah-TUR-nuh-ri) - Tertiary (TUR-shi-ri) - -While the units discussed above are the major divisions of geologic -_time_, the geologist usually works with smaller units of _rocks_ called -_formations_. A geologic formation is identified and established on the -basis of definite physical and chemical characteristics of the rocks. -Formations are usually given geographic names which are combined with -the type of rock that makes up the bulk of the formation. For example, -the Beaumont clay was named from clay deposits that are found in and -around Beaumont, Texas. - - - - - THE GEOLOGY OF TEXAS - - -The geologic history of Texas, like the geologic history of the rest of -the earth, is recorded primarily in marine sedimentary rocks. These -rocks provide some knowledge of the early geography and the first -inhabitants of what is now the State of Texas. Most of these rocks were -formed from sediments deposited in shallow seas which covered parts of -the State at various times in earth history. - -By studying these rocks and their relations to each other, geologists -have established a geologic column for Texas. - - - Physiography - -In order to discuss the distribution and exposures of the rocks of -Texas, it is helpful to be familiar with the _physiography_ of the -State. Physiography deals with the study of the origin and description -of land forms, such as mountains, valleys, and plains. Plate 9 is a map -of Texas which shows the major physiographic provinces within the State. - -The majority of the land forms in Texas have been produced by the -processes of erosion attacking the structural features of an area. -Certain other land forms may be related to the effects of igneous -activity which resulted in the accumulation of large masses of igneous -rocks. The Davis Mountains are an example of surface features produced -in this manner. - -In discussing the physiography of Texas, three major physiographic -provinces will be recognized. These are (1) the Trans-Pecos region, (2) -the Texas Plains, and (3) the Gulf Coastal Plain (Pl. 9). - - - TRANS-PECOS REGION - -The Trans-Pecos region, located in the westernmost part of the State, is -an area of mountains and plateaus with broad basins between the major -mountain ranges. Many different types of rocks are exposed in -Trans-Pecos Texas and these include marine, fresh-water, and terrestrial -deposits. In many areas igneous rocks flowed out on the surface and now -overlie sedimentary rocks. There are also many places where igneous -rocks have been injected into the surrounding rocks, and these igneous -rocks have been exposed by later erosion. - -Included within this area is the Van Horn uplift of southern Hudspeth -and Culberson counties, the Solitario uplift of southern Presidio and -Brewster counties, and the Marathon uplift of northeast Brewster County. -This region also includes the Big Bend area of Texas, a part of which -has been set aside as a National Park where many interesting and -important geological features may be seen. - -The Trans-Pecos region is one of rugged topography with elevations as -high as 8,700 feet, at Guadalupe Peak in the Guadalupe Mountains of -northern Culberson County, and as low as 1,500 feet, in the Rio Grande -valley. - -Numerous invertebrate fossils occur in the Cretaceous limestones and -shales of the Trans-Pecos region and in the Paleozoic rocks of the -Marathon uplift. The Gaptank formation of Pennsylvanian age and the -Permian reef limestones of the Glass Mountains are especially -fossiliferous. In addition, many vertebrate fossils have been collected -in Trans-Pecos Texas, particularly in and around Big Bend National Park. - - - TEXAS PLAINS - -The plains of Texas are broad expanses of country with very little -surface relief. Most of the plains support grasses and some have wooded -areas, particularly along stream valleys. - -The plains of the northwestern part of the State have been subdivided as -follows. - - - High Plains - -This area (Pl. 9), often called “the caprock,” is an elevated plateau -which rises above the rolling plains which surround it. The High Plains -are bounded by the Pecos River valley on the south, southeast, and west -and by the North-Central Plains on the east. - -The surface of the High Plains is very flat and characterized by a -sparse cover of grasses and few trees. The surface strata consist -largely of unconsolidated deposits of sands and gravels of Quaternary -and Tertiary age, with remnants of Lower Cretaceous limestones along the -southern margin. The rocks of the High Plains are mostly -unfossiliferous, but mammalian remains have been found at several -localities. - - [Illustration: Plate 9 - Physiographic map of Texas.] - - HIGH PLAINS - NORTH-CENTRAL PLAINS - GRAND PRAIRIE - TRANS-PECOS TEXAS - VAN HORN UPLIFT - THE BIG BEND AREA - SOLITARIO UPLIFT - MARATHON UPLIFT - EDWARDS PLATEAU - LLANO UPLIFT - BALCONES FAULT ZONE - GULF COASTAL PLAIN - - - North-Central Plains - -Surface strata of the North-Central Plains (Pl. 9) are westward-dipping -Pennsylvanian, Permian, and Triassic rocks. Present also are extensive -exposures of Quaternary sands and gravels which trend north-south across -the central portion of the region. The area is bounded on the west by -the High Plains, on the east by the Grand Prairie, and on the south by -the Edwards Plateau and Llano uplift. Many vertebrate fossils have been -collected from the Permian and Triassic rocks of this area. There are -also many excellent outcrops of fossiliferous Pennsylvanian formations -in the North-Central Plains region. - - - Edwards Plateau - -The Edwards Plateau (Pl. 9) is located in south-central Texas and is -bounded on the south by the Balcones fault zone and on the north by the -North-Central Plains. The surface of the area is typically flat with a -gentle slope to the south. The rocks of the Edwards Plateau consist -primarily of Lower Cretaceous limestones and shales, many of which are -very fossiliferous. - - - Grand Prairie - -This area (Pl. 9) has a relatively flat surface but there are areas of -gently rolling hills. The eastern boundary of the Grand Prairie is -marked partly by the Balcones fault zone. North of McLennan County, -however, the Balcones fault zone is not expressed at the surface and in -this area the eastern boundary is defined by the western edge of the -Woodbine exposures. Upper and Lower Cretaceous rocks occur at the -surface and dip to the southeast; many of these rocks contain a large -number of invertebrate fossils. - - - Llano Uplift - -The Llano uplift (Pl. 9) is located in the central part of the State -where Precambrian igneous and metamorphic rocks and sedimentary rocks of -early Paleozoic age occur on the surface. The area, which now appears as -a basin-shaped depression, was at one time covered by Lower Cretaceous -rocks and perhaps also by Devonian, Mississippian, and Pennsylvanian -strata. These have since been removed by erosion. The east, south, and -west sides of the uplift are surrounded by Lower Cretaceous rocks, and -the northern margin is marked by the Mississippian and Pennsylvanian -formations of the North-Central Plains. The area is, in general, -composed of unfossiliferous rocks, but some invertebrate fossils -(primarily trilobites and brachiopods) have been collected. - - - GULF COASTAL PLAIN - -The Gulf Coastal Plain (Pl. 9) is composed of Cretaceous, Tertiary, and -Quaternary rocks and includes the eastern, southeastern, and southern -portions of the State. The rocks of the area consist of sands, clays, -shales, and limestones. The Texas Gulf Coastal Plain is bounded on the -north and west by the Balcones fault zone, on the south and southwest by -the Gulf of Mexico, and extends eastward into Arkansas and Louisiana. - -The region has broad river valleys and uplands of low relief, but there -is an increase in relief toward the interior of the State. The surface -of the area slopes gradually toward the Gulf and successively younger -formations are encountered gulfward. - -The rocks of the Texas Gulf Coastal Plain are relatively -unfossiliferous, but many of the Upper Cretaceous rocks contain fossils. -In the central portion of the region some marine formations of Tertiary -age locally contain well-preserved invertebrate fossils. - - - - - Geology - - -Geologic studies of the State of Texas have indicated the presence of -rocks formed during every era and period of geologic time. These range -from the Precambrian granites of the Llano uplift to the Quaternary -gravels of the High Plains. - - [Illustration: Plate 10 - GENERALIZED GEOLOGIC MAP OF TEXAS - Modified from Geologic Map of Texas, 1933] - -One of the best ways to become acquainted with the geology of Texas is -to study the _geologic map_ of the State (Pl. 10). A geologic map shows -the distribution and age of surface rocks and may also indicate what -kind of geologic structures are present. The types of rocks that crop -out at the surface may be shown by means of symbols, colors, or -patterns, and these are explained by a legend which accompanies the map. -On Plate 10, colors are used to show the distribution and geologic age -of the surface rocks of Texas. Reference to this map will give the -collector some idea of the age of the fossils that might be found in a -given area. Some special geologic maps may have the location of geologic -structures and formation contacts indicated by means of symbols, such as -dashed lines, arrows, and similar special markings. However, the map -included in this publication does not show any of these special -markings. - - - PRECAMBRIAN ROCKS - -The Precambrian rocks of Texas are composed of igneous and metamorphic -rocks and some sedimentary rocks. Most of the Precambrian outcrops are -in the Llano uplift and El Paso and Van Horn regions. - -Alterations produced by vast amounts of time, heat, and pressure have -obliterated any trace of fossils that may have been present in these -rocks. With the exception of some questionable primitive plants -collected in the Van Horn region, no Precambrian fossils have been -reported from Texas. - - - PALEOZOIC ROCKS - -Rocks of Paleozoic age are widespread in Texas, and rocks of each period -are well exposed. Outcrops are found in the Llano uplift, North-Central -Plains, and Trans-Pecos region. The most extensive exposures are of -Pennsylvanian and Permian age, and the former are highly fossiliferous -in parts of the North-Central Plains. - - Cambrian - -Rocks of late Cambrian age are exposed in the Llano, Marathon, and -Solitario uplifts, and the Franklin Mountains near El Paso. These are -sedimentary rocks consisting of conglomerates, sandstones, shales, -limestones, and some dolomites. - -Some of these formations are relatively fossiliferous, but the specimens -are commonly fragmental and very poorly preserved. Fossils that are apt -to be found in the Cambrian rocks of the Llano uplift include -brachiopods, gastropods, trilobites, and small rounded objects believed -to have been formed by algae (primitive one-celled plants). In other -parts of the State, Cambrian rocks are sparsely fossiliferous and the -fossils consist primarily of fragmental brachiopods, trilobites, and -algae. - - Ordovician - -Ordovician outcrops are present in the Llano uplift of central Texas and -in the Marathon, Solitario, El Paso, and Van Horn regions of Trans-Pecos -Texas. These are sedimentary rocks and consist largely of sandstones, -cherts, limestones, and dolomites. - -Although some of the Ordovician formations are fossiliferous, they are -seldom collected by amateur paleontologists because they are exposed in -relatively inaccessible places and the fossils are usually poorly -preserved. Ordovician fossils reported from Texas include sponges, -corals, brachiopods, gastropods, cephalopods, and trilobites. In -addition, the Marathon formation of the Marathon uplift contains large -numbers of well-preserved graptolites (fig. 24, p. 86). - - Silurian - -The Silurian of Texas is poorly represented in surface exposures, and -only one formation, the Fusselman, has been described. The Fusselman -crops out in the El Paso and Van Horn regions where it is a white -dolomitic limestone. Fossils are not abundant in this formation, but -brachiopods and corals have been collected at a few localities. - - Devonian - -Devonian rocks are best developed in Trans-Pecos Texas, especially in -the Marathon, El Paso, and Van Horn regions. In addition to the -Trans-Pecos exposures, there are minor outcrops of Devonian rocks in the -Llano uplift of central Texas. - -Fossils are rare and fragmental in the Trans-Pecos exposures and consist -primarily of radiolarians and brachiopods. The Devonian rocks of central -Texas are predominantly calcareous and, although the material is usually -poorly preserved, many fossils have been collected from them. These -include bryozoans, corals, brachiopods, gastropods, and trilobites. -Conodonts and fragments of primitive armored fishes (Pl. 37) have also -been reported. - - Mississippian - -Mississippian rocks are exposed in the Llano region and in the Hueco -Mountains of the Trans-Pecos area. The Trans-Pecos rocks primarily -contain brachiopods with some bryozoans and gastropods. - -The central Texas Mississippian rocks are much more fossiliferous and -some of the material is well preserved. Fossils reported from this area -include brachiopods (Pl. 17), crinoids, gastropods, cephalopods, -trilobites, and ostracodes. - - Pennsylvanian - -Pennsylvanian rocks are well represented in Texas and are exposed in the -Llano uplift, north-central Texas, and Trans-Pecos Texas. - -In Trans-Pecos Texas fossiliferous rocks crop out in the Hueco and -Diablo Mountains. Fossils found in this area are algae, fusulinids, -corals, brachiopods, pelecypods, gastropods, cephalopods, and crinoids. -There is also a thick section of Pennsylvanian rocks in the Marathon -uplift, but only one formation, the Gaptank, is very fossiliferous. It -contains many fossils including fusulinids, sponges, corals, bryozoans, -brachiopods, gastropods, pelecypods, cephalopods, and crinoids. - -Certain Pennsylvanian strata in the Llano region are very fossiliferous, -and the material is well preserved. The more abundant forms are -fusulinids, corals, brachiopods, gastropods, pelecypods, cephalopods, -and crinoids. - -Probably the best Pennsylvanian collecting areas are to be found in -north-central Texas. Here the thick marine limestones and shales contain -large numbers of well-preserved invertebrate fossils, and the -terrestrial or shallow marine strata have yielded an abundance of plant -fossils. Invertebrate fossils are apt to be found along the banks of -streams and gullies and in railroad and highway cuts. Many of the -limestones bear large numbers of fusulinids or crinoid stems, and the -shales may contain many corals, brachiopods, and mollusks. The best -collecting will, of course, be found where the rocks have been -sufficiently weathered. - - [Illustration: Fig. 8. Sketch of typical crinoidal limestone from the - Pennsylvanian of north Texas.] - -Typical invertebrate fossils are foraminifera (principally fusulinids), -corals (especially the solitary or “horn” corals), brachiopods, -bryozoans (the lacy and branching types are most common), pelecypods, -gastropods (exhibiting a variety of coiling), cephalopods (nautiloids -and goniatites predominate), and crinoids, which in many areas are found -in thick crinoidal limestones (fig. 8). Some typical Pennsylvanian -fossils are illustrated in Plates 14, 15, 17, 18, 19, 20, 21, 24, 32, -and 35. - - Permian - -Permian rocks are found in widely separated areas in Texas. The best -exposed section of marine Permian rocks is found in the Glass Mountains -of Brewester County, and many of these rocks are very fossiliferous. The -original shell material of some of the Permian fossils of this area has -been replaced by siliceous material which is very well preserved. These -silicified fossils are removed from the limestone by solution in acid, -and some most remarkable specimens have been recovered in this manner -(Pl. 3). Brachiopods are the most common fossils, but corals, bryozoans, -and mollusks have also been recovered. - -Extensive Permian exposures occur also in the central part of the -North-Central Plains region. These rocks were formed from sediments of -both marine and continental origin and some of them are fossiliferous. -The marine rocks contain a variety of invertebrate fossils including -brachiopods, pelecypods, gastropods, and ammonoids. Those rocks -representing terrestrial deposits contain vertebrate remains at many -localities, and numerous amphibians and primitive reptiles (Pl. 40) have -been collected from them. - - - MESOZOIC ROCKS - -Mesozoic rocks occur over a wide area of Texas and include exposures of -Triassic, Jurassic, and Cretaceous age. Many of the Upper and Lower -Cretaceous outcrops are quite fossiliferous and easily accessible and -thus of considerable interest to many amateur collectors. - - Triassic - -Triassic rocks crop out in parts of the High Plains, the Glass Mountains -of Trans-Pecos Texas, and parts of Pecos, Crockett, Upton, Reagan, and -Glasscock and other west Texas counties. These are predominantly -nonmarine rocks consisting of conglomerates, sandstones, shales, and -some gypsum beds. - -Triassic fossils are almost exclusively vertebrates, although some -poorly preserved plant and invertebrate remains have been reported. -Fossil vertebrates of the Texas Triassic include phytosaurs (Pl. 42), -crocodiles, amphibians, and fish. - - Jurassic - -In Texas, surface exposures of Jurassic rocks are known only from Malone -Mountain in southwestern Hudspeth County. The rocks there are -limestones, shales, sandstones, and conglomerates. Fossils reported from -that locality include marine and fresh-water pelecypods, fresh-water -gastropods, and ammonites. - - Cretaceous - -Rocks of Cretaceous age are widely distributed in Texas and represent -one of the more important rock systems of the State. Cretaceous outcrops -occur in central Texas, north Texas, the Edwards Plateau, parts of the -High Plains, the Gulf Coastal Plain, and Trans-Pecos Texas. - -As mentioned earlier, the Texas Cretaceous has been divided into the -Lower Cretaceous (Comanche series) and Upper Cretaceous (Gulf series). -These rocks consist primarily of marls (a type of calcareous clay), -shales, chalks, and limestones, but sands and conglomerates also occur. -Cretaceous rocks occur on the surface of about 28 percent of Texas, and -many of the larger cities of the State are situated on Cretaceous -strata. - -Many of the Gulf and Comanche formations contain fossils which are of -interest both to amateur and professional paleontologists. Because of -their wide distribution in and near large population centers, Cretaceous -outcrops can be conveniently visited by many amateur fossil collectors. -The fossils are usually abundant and varied, and some are well -preserved. Although numerous kinds of fossils may be collected, the more -common forms are cephalopods, pelecypods, gastropods, and echinoids. -Some of the more typical Cretaceous fossils are shown in Plates 16, 21, -25-28, 32, 33, 35, and 36. - -Cretaceous fossils are more commonly found in shales and chalky -limestones. Fossiliferous outcrops of these rocks can be found along -many streams, roads, and highways of central Texas, north Texas, and the -Edwards Plateau. Outcrops which have been weathered are more likely to -provide good collecting. In general, collecting is poor in areas covered -with heavy vegetation or recent stream deposits. Good collecting -localities are outcrops which have a fairly steep slope with a covering -of weathered rock material and a minimum of vegetation. One should move -slowly from the base of the slope upward while searching the ground for -any evidence of fossils, and particular attention should be given to any -small gullies since these often contain fossils that have been washed -out of upper beds in the exposure. - - - CENOZOIC ROCKS - -Cenozoic rocks are widespread in Texas but occur primarily in a broad -belt along the Gulf Coastal Plain. In addition, there are exposures of -nonmarine Cenozoic strata in the High Plains, North-Central Plains, and -Trans-Pecos region. There are also many exposures of Cenozoic igneous -rocks in Trans-Pecos Texas. - -Rocks of Cenozoic age occur in more than one-third of Texas and consist -of conglomerates, sands, clays, and some limestone and lignite beds. - - - Tertiary - -Extensive exposures of Tertiary rocks trend northeast-southwest in a -broad band across the Gulf Coastal Plain area. These strata, consisting -of sands, clays, and poorly consolidated limestones, are underlain by -Cretaceous rocks. - -Invertebrate fossils are common in certain Tertiary formations and -pelecypods, gastropods, and corals are the predominant forms. In -general, however, fossiliferous exposures are of local occurrence and -most of the Tertiary formations are unfossiliferous. Those Tertiary -invertebrates that are present, however, are often well preserved and -represent many interesting types (Pls. 16, 22, 23, 29, 30, 31). - -Tertiary invertebrate fossils are commonly found in sands, clays, and -marls. Many of these sands and marls have a green color which is due to -the presence of glauconite (a green mineral containing iron and closely -related to the micas). At certain localities on the Gulf Coastal Plain -the glauconite marls and sands of the Weches and Crockett formations -contain large numbers of well-preserved clams, snails, and corals. -Fossiliferous exposures of Tertiary rocks are sometimes found in road -cuts, but better exposures may be found along the banks of rivers and -creeks. Certain bluffs along the Brazos, Sabine, and Trinity rivers are -well-known Tertiary fossil collecting localities. Many of these better -localities are listed in some of the Bureau of Economic Geology -bulletins included in the bibliography of this publication (pp. -109-110). - - - Quaternary - -Quaternary deposits of Pleistocene age (geologic time scale, Pl. 1) are -found in many parts of Texas and consist of sands, clays, and gravels. - -These rocks are distributed along the Gulf Coast in a belt from 50 to -100 miles wide. They occur also as stream terraces in the Edwards -Plateau and North-Central Plains regions. In addition, Quaternary sands -and gravels are widely distributed over the surface of much of -Trans-Pecos Texas. There are also fossiliferous Pleistocene strata in -the High Plains region. - -Invertebrate fossils are rare in Pleistocene rocks, but some fresh-water -and terrestrial mollusks occur. Vertebrate remains, however, are -abundant in many localities, and large numbers of horses, camels, -mammoths, and other mammals (Pls. 46-49) have been collected. Fossil -bones and teeth (figs. 25, 26, p. 104) are commonly found in the gravels -and sands of many of the river terraces of the State. - - - - - MAIN TYPES OF FOSSILS - - -The beginning fossil collector is usually amazed by the many different -plants and animals that have left some trace of their existence. In -order to understand these different types of prehistoric life, it is -necessary to know something about the organisms that are living today. - -This handbook discusses the more important groups of plants and animals -which have left some sort of paleontological record, and each major -group begins with a discussion of the more simple organisms and -continues through the more advanced forms. Because scientific workers do -not always agree on exactly the same classification, the system adopted -in this handbook contains the latest ideas of several workers. It is -simple enough to understand, yet complete enough to help one know and -classify his fossils. It should be noted that this classification may -differ in some respects from that of certain older paleontological -publications. Therefore, it has seemed advisable to list other names for -some of the groups that are discussed. - -In some instances, the brief descriptions and illustrations of each -group will enable the collector to make a preliminary identification of -his fossils. For more detailed information about each group, the reader -should refer to “Books About Fossils” (pp. 108-110). - -This part of the handbook begins with a brief summary of the major -groups of the plant kingdom, followed by a discussion of the -characteristics and relative paleontological importance of the various -invertebrate animals. Emphasis is placed on the invertebrates because -this type of fossil is most commonly collected by the amateur. Finally, -there is a general review of the vertebrates. - - - - - PLANT FOSSILS - - -Plant fossils are usually fragmental and poorly preserved, and this -tends to discourage most amateurs from an active interest in -paleobotany. However, in spite of these problems, much is known of the -evolution of plants, and plant fossils provide much information about -life of the past. In addition, certain plants are of considerable value -as indicators of ancient climatic conditions, and their remains have -played a large part in the formation of vast coal deposits. - - - Classification of the Plant Kingdom - -In the following classification only the larger taxonomic groups are -discussed. Notice that the term _division_ has been used in place of the -term phylum as used in the animal kingdom. This usage is now preferred -by many botanists and paleobotanists. - - DIVISION THALLOPHYTA - -Thallophytes are simple plants without roots, stems, or leaves. They -include the fungi, algae, and diatoms (Pl. 12). Diatoms are microscopic -fossils that are found in many of the rocks of Texas, and they are quite -abundant in Recent sediments as well. Certain of the Paleozoic -limestones of central Texas contain banded spherical masses of algae -called “algal biscuits.” Although not particularly useful fossils, -thallophytes have a long geologic history and are known in rocks ranging -from Precambrian to Recent in age. - - DIVISION BRYOPHYTA - -The bryophytes are simple rootless plants and include the mosses and -liverworts. Although more complex, the bryophytes resemble the algae in -some respects. They are uncommon fossils, but undoubted bryophytes -(liverworts) have been reported from rocks as old as Mississippian. - - DIVISION TRACHEOPHYTA - -This division has been divided into four subdivisions, among which are -many of the more common living and fossil plants. Such important plants -as the ferns, evergreens, hardwood trees, and the flowering plants are -all tracheophytes. Among the more common and abundant fossil -tracheophytes are the ferns, cycads, and _Gingko_, in addition to such -important “coal plants” as the scale trees, club mosses, and scouring -rushes (Pls. 12, 13). The latter commonly occur in many of the world’s -great coal deposits, and their remains make up a large part of the coal. -Plant fossils of this type may be collected in the dumps around some of -the abandoned coal mines in north-central Texas and from other -Pennsylvanian rocks in north and Trans-Pecos Texas. - - [Illustration: Plate 11 - GEOLOGIC RANGE OF THE MAJOR GROUPS OF PLANTS AND ANIMALS - The bands give some indication of the geologic range and relative -abundance of the major groups of plants and animals. An increase in the - width of the range band corresponds to a relative increase in numbers - during the corresponding portion of geologic time.] - - PRECAMBRIAN - PALEOZOIC - CAMBRIAN - ORDOVICIAN - SILURIAN - DEVONIAN - MISSISSIPPIAN - PENNSYLVANIAN - PERMIAN - MESOZOIC - JURASSIC - CRETACEOUS - CENOZOIC - - Thallophyta - Bryophyta - Tracheophyta - Protozoa - Porifera - Coelenterata - Bryozoa - Brachiopada - Mollusca - Annelida - Arthropoda - Echinodermata - Chordata - - [Illustration: Plate 12 - FOSSIL PLANTS] - - [Illustration: THALLOPHYTES] - - DIATOMS × 900 - ALGAE × 400 - - [Illustration: TRACHEOPHYTES] - - LEPIDODENDRON × ½ - SIGILLARIA × ½ - - [Illustration: Plate 13 - FOSSIL PLANTS - TRACHEOPHYTES] - - NEUROPTERIS × ½ - PSILOPHYTON × ⅓ - CALAMITES × ½ - AMELANCHIER × ½ - CORDAITES × ¼ - GINGKO × ½ - -Fairly well-preserved plant remains may also be collected from the -Woodbine group of the Upper Cretaceous in north Texas, and fossil wood, -most of it silicified, has been reported from rocks of almost all ages -and in almost every section of the State. In addition, some of the -carbonaceous clays and shales of east Texas contain large assemblages of -plant leaves, which in some places are well preserved. - -It is also possible to find the fossilized remains of seeds, spores, and -pollen. Because of their small size, these minute remains are not -destroyed by the drill bit and can be brought out of deep wells without -being damaged, and for this reason they are a valuable tool for the -micropaleontologist. - - - - - ANIMAL FOSSILS - - -The fossilized remains of animals are very common in many of the -sedimentary rocks of Texas. These remains are of many different kinds -and represent the fossils of such diverse organisms as the shell of a -tiny one-celled animal or the bones or tusk of a huge elephant. The -fossils most commonly found, however, are the remains of invertebrate -animals such as clams, snails, and corals, and it is this type of fossil -that attracts the interest of most amateur collectors. - -It is not always easy to tell whether certain organisms are plants or -animals, and because of this some scientists have suggested that these -“in-betweens” be placed in a separate kingdom—the Protista. The -protistans are primarily unicellular organisms and are represented by -such forms as bacteria, algae, diatoms, and the protozoans (see below). -But in this publication, only the plant and animal kingdoms are -recognized. - - - Phylum Protozoa - -This phylum is composed of simple one-celled animals many of which have -no shell or external body covering. Some, however, have external hard -parts that can become fossilized, and these forms are quite useful -microfossils. - - CLASS SARCODINA.— - -This class contains a group of one-celled animals which may secrete an -exoskeleton (external protective covering) of chitin, silica, or calcium -carbonate. Included in this class are foraminiferans (commonly called -forams) and radiolarians. - - Order Foraminifera.— - -Members of this order secrete tiny chambered shells which are very -useful microfossils. The forams are predominantly marine organisms and -have shells composed of chitin, silica, or calcium carbonate. In -addition, some forms construct a shell of sand grains or some other -material which is cemented together by a sticky substance that is -secreted by the animal. - -Forams are very abundant in the rocks of Texas and particularly so in -rocks of Mesozoic and Cenozoic age. The most numerous and easily -observed Paleozoic foraminiferans are the fusulinids (fig. 9a), and -their small spindle-shaped remains are very abundant in many of the -Pennsylvanian limestones of north-central and Trans-Pecos Texas. Some -typical Texas forams are illustrated in figure 9. - - Order Radiolaria.— - -The radiolarians (fig. 10) have delicate spine-covered shells composed -of silica, and their remains are very abundant in certain recent marine -sediments. They may also be found as fossils and have been reported from -Devonian and Permian rocks in Trans-Pecos Texas, and probable -radiolarians have been reported from still younger beds. - - [Illustration: Fig. 9. Typical Texas Foraminifera (all greatly - enlarged). (a) _Fusulina_ (Pennsylvanian). (b) _Robulus._ (c) - _Globigerina._ (d) _Frondicularia._ (b-d, Cretaceous).] - - [Illustration: Fig. 10. Typical radiolarians (greatly enlarged). (a) - _Actinomma_ (Recent). (b) _Porodiscus_ (Eocene).] - - - Phylum Porifera - -These are sponges and are the simplest of the many-celled animals. -Living sponges secrete a skeleton which may be composed of chitin, -silica, or calcium carbonate. These substances are commonly found in the -form of spicules—tiny hard parts that are used to help support the soft -tissues of the animal. These spicules take on a variety of shapes (Pl. -14) and are occasionally found as microfossils in some marine sediments. - -Although sponges are not particularly common fossils, their remains -occur in some parts of the State. Sponges have been collected from -Paleozoic and Mesozoic formations of north and Trans-Pecos Texas, and -their spicules have been reported from well cuttings. - - - Phylum Coelenterata - -The coelenterates are multicelled animals which, though more complex -than the sponges, are rather primitive animals. The living animal is -characterized by a sac-like body cavity, a definite mouth, and tentacles -which bear stinging cells. Some forms, for example, the jellyfishes, -have an umbrella-shaped body and are single free-moving organisms. -Others, like the colonial corals, are composed of many individuals -living together in a colony. - -Most zoologists and paleontologists recognize three classes of -coelenterates: (1) the Hydrozoa, containing the small animals known as -hydroids, (2) the Scyphozoa, which includes the jellyfish, and (3) the -Anthozoa, which includes the corals and sea anemones. Because of their -extreme fragility and lack of hard parts, hydrozoans and scyphozoans are -not commonly found as fossils. They do, however, have a long geologic -history and may be preserved when unusual conditions of fossilization -occur. The anthozoans, especially the corals, are by far the most -important class geologically, and these forms have left a very good -paleontological record. - - CLASS ANTHOZOA.— - -This class is composed of a group of exclusively marine organisms and -includes the corals and sea anemones. The coral animal, or _polyp_, -secretes a cup-shaped calcareous (limy) exoskeleton. This skeleton, -called a _corallite_, is usually divided by radial partitions called -_septa_. The polyp lives in the _calyx_, which is the central -bowl-shaped depression in the top of the corallite (fig. 11a). - -_Solitary_ corals form an individual corallite for each polyp, and -because of their shape these may be given such names as “horn corals” -(_Lophophyllidium_, Pl. 15) or “button corals” (_Micrabacia_, Pl. 16). -_Colonial_ or _compound_ corals (Pl. 15) live together in colonies, -which are formed of many individual skeletons attached to each other -(fig. 11b), and the compound mass of coral skeletons formed in this -manner is called a _corallum_. Fossil corals commonly occur in many -marine limestones and in places constitute a large portion of the rock. - - [Illustration: Fig. 11. Morphology and principal parts of corals. (a) - Solitary or “horn” coral. (b) Colonial or compound coral.] - - a - Columella - Septum - Corallite - b - Calyx - Septum - Corallum - -The class Anthozoa has been divided into several subclasses, but only -one, the Zoantharia, is of paleontological importance. - - Subclass Zoantharia.— - -Most corals and all sea anemones belong to this subclass. Zoantharians -are either colonial or solitary and, because most of them possess a hard -preservable exoskeleton, they are the most important group of anthozoans -geologically. The various orders of the subclass Zoantharia are -discussed below. - - Order Rugosa.— - -These are corals in which the septa are arranged in cycles of four. Both -solitary and colonial forms occur, and they are found only in rocks of -Paleozoic age. Rugose corals are abundant in many of the Paleozoic -formations of Texas, and two of the more typical forms -(_Lophophyllidium_ and _Caninia_) are illustrated in Plate 15. Members -of this order have been placed in the subclass Tetracoralla of older -classifications. - - Order Scleractinia.— - -The scleractinians are solitary or colonial corals in which the septa -grow in multiples of six, and they are the most important and abundant -of the modern corals. These corals were the dominant reef builders of -Mesozoic and Cenozoic seas, and their remains are common in many of the -marine formations of the State. Plate 16 illustrates some typical -scleractinian corals from the rocks of Texas. This order has also been -referred to as subclass Hexacoralla, and its members have been called -hexacorals. - - Order Tabulata.— - -These are corals that are now extinct but are known from fossils in both -Paleozoic and Mesozoic rocks. Tabulate corals are characterized by -horizontal partitions called _tabulae_, and septa are absent or poorly -developed. The tabulates were the most abundant reef-building corals -during Paleozoic time and are well known as fossils. Because of certain -similarities with other anthozoans, some paleontologists have treated -the Tabulata as a distinct subclass rather than as an order of the -Zoantharia. - -Tabulate corals are not uncommon in many of the Paleozoic rocks of -Texas, and two of these (_Cladochonus_ and _Striatopora_) are -illustrated in Plate 15. - - - Phylum Bryozoa - - [Illustration: Fig. 12. Two types of bryozoans or “moss animals.” (a) - Section of the lacy type bryozoan. (b) The spiral axis of _Archimedes_ - (Mississippian).] - -Bryozoans are colonial animals that are often referred to as “sea mats.” -They have been called this because they are commonly found matted on -shells, rocks, fossils, and other objects. The living animal is quite -small, has a tentacle-bearing ridge surrounding the mouth, and secretes -a tiny cup-like exoskeleton composed of calcareous or chitinous -material. These little chambers, known as _zooecia_ (or _autopores_), -are seen as small pits on the surface of the bryozoan colony -(_Rhombopora_, Pl. 17). The zooecia grow together to form the bryozoan -colony, and some fossil colonies grow to be as much as 2 feet across. -Such colonies may be spiral (fig. 12b), branching, or lace-like (fig. -12a), and the latter two types are very common in many of the -fossiliferous strata of Texas. Undoubted bryozoan fossils have been -recorded in rocks of Lower Ordovician age, but questionable Cambrian -forms have also been reported. Bryozoans are abundant in the seas of -today, but only a few forms inhabit fresh waters. - - [Illustration: Plate 14] - - [Illustration: SPONGE SPICULES - (GREATLY ENLARGED)] - - [Illustration: PALEOZOIC SPONGES] - - MEANDROSTIA × 1 - HELIOSPONGIA × 1 - ASTRAEOSPONGIUM × ½ - ASTYLOSPONGIA × ½ - RECEPTACULITES × ½ - GIRTYOCOELIA × 2 - - [Illustration: Plate 15 - PENNSYLVANIAN CORALS] - - CLADOCHONUS × 1 - STRIATOPORA × 1 - LOPHOPHYLLIDIUM PROLIFERUM × 1 - MICHELINIA × 1 - CANINIA × 1 - LOPHOPHYLLIDIUM RADICOSUM × 1 - - [Illustration: Plate 16] - - [Illustration: CRETACEOUS CORALS] - - CLADOPHYLLIA × 1 - PARASMILIA × 1 - PLEUROCORA × 1 - - [Illustration: TERTIARY CORALS] - - ENDOPACHYS × 1 - ASTRHELIA × 1 - FLABELLUM × 1 - MICRABACIA × 2 - TROCHOSMILIA × 1 - -In Texas one may expect to find bryozoan remains in the Pennsylvanian -rocks of north-central and Trans-Pecos Texas where they are abundant in -certain of the marine shales and limestones. Bryozoans may also be -collected from some Cretaceous and Tertiary beds, but their remains are -small and fragmental and they are easily overlooked. Bryozoans have also -been found matted on the shells of fossil mollusks and other -invertebrates. - - - Phylum Brachiopoda - -The brachiopods are a large group of exclusively marine organisms with -shells composed of two pieces called _valves_ (fig. 13). These valves -are usually composed of calcareous or phosphatic material and enclose -and protect the soft parts of the brachiopod animal. The soft parts are -composed of muscles, the _mantle_ (which secretes the valves), -digestive, respiration, reproductive, and excretory organs, and the -tentacle-bearing _lophophore_. - -In adult life the brachiopod is attached to the sea bottom by means of a -fleshy stalk called the _pedicle_ (fig. 14), and this is usually -extruded through a hole (the _pedicle foramen_) which is located in the -_ventral_ or _pedicle_ valve. The upturned area which is usually present -on the pedicle valve is called the _beak_. The other valve, known as the -_dorsal_ or _brachial_ valve, is usually the smaller of the two (fig. -13b). The two valves are opened by means of muscles, and since death -results in relaxation of these muscles, fossil brachiopods are typically -found with valves closed. - -Brachiopods vary greatly in size and shape and exhibit a wide variety of -ornamentation, such as spines, ribs, nodes, and other structures. They -are abundant fossils in many of the Paleozoic rocks of Texas but are -relatively rare in Mesozoic and Cenozoic formations. - -The phylum has been divided into two subclasses, the Inarticulata and -the Articulata. This classification is based upon the nature of the -_hinge-line_—the edge of the shell where the two valves articulate. - - [Illustration: Fig. 13. Morphology and principal parts of articulate - brachiopods.] - - a - Pedicle foramen - Hinge line - b - Pedicle valve - Beak - Brachial valve - - CLASS INARTICULATA.— - -The members of this class are rather primitive and have a long geologic -history. These brachiopods have valves which are not provided with hinge -teeth, the valves being held together by muscles, and a hinge-line is -lacking (fig. 14). Most inarticulate brachiopods are circular or -tongue-like in shape and commonly composed of chitinous and phosphatic -material. Inarticulate brachiopods range from Lower Cambrian to Recent -in age but were never as common as the articulate brachiopods, which are -described below. Brachiopods belonging to this class have been recorded -from several Paleozoic formations in Texas (Pl. 17, _Lingula_, -_Apsotreta_, _Angulotreta_). - - [Illustration: Plate 17] - - [Illustration: PENNSYLVANIAN BRYOZOANS] - - FISTULIPORA × 6 - POLYPORA × 5 - RHOMBOPORA × 8 - - [Illustration: CAMBRIAN BRACHIOPODS] - - APSOTRETA × 10 - LINGULA × 4 - ANGULOTRETA × 10 - - [Illustration: MISSISSIPPIAN BRACHIOPODS] - - RHIPODOMELLA × 1 - DICTYOCLOSTUS × 1 - CAMAROTOECHIA × 1 - - [Illustration: Fig. 14. _Lingula_, a typical Recent inarticulate - brachiopod showing extended pedicle.] - - Pedicle - Valve - - CLASS ARTICULATA.— - -Articulate brachiopods have a well-defined hinge-line (fig. 13a). One -valve has well-developed teeth which articulate with sockets in the -opposing valve, and there is a well-developed muscle system which aids -in opening and closing the shell. Articulate brachiopods are -characterized by calcareous shells which are typically of unequal size -and a wide variety of shapes (Pls. 18, 19). The class has been divided -into several orders which have been established primarily on the nature -of the pedicle foramen and the nature of shell growth. - -Articulate brachiopods range from Lower Cambrian to Recent in age and -are particularly abundant in certain Pennsylvanian formations of -north-central and Trans-Pecos Texas. They are also present in certain -other fossiliferous strata of Paleozoic age but are less abundant and -not as well preserved. The only Cretaceous brachiopod that is found in -large numbers is _Kingena wacoensis_ (Roemer) (fig. 15), which is -particularly abundant in certain formations in the upper part of the -Comanche series. - - [Illustration: Fig. 15. _Kingena wacoensis_, a common Cretaceous - brachiopod. (a) Dorsal view. (b) Lateral view. (c) Ventral view.] - - - Phylum Mollusca - -The phylum Mollusca encompasses a large group of aquatic -(water-dwelling) and terrestrial (land-dwelling) invertebrates which -includes such familiar forms as the snails, clams, oysters, squids, and -octopuses. Most mollusks possess a calcareous shell that serves as an -exoskeleton, and these hard parts are well adapted for preservation as -fossils. However, some mollusks (the slugs) have no shells, and others -(the squids) have an internal calcareous shell. Because of their -relative abundance and great variety, mollusks are particularly useful -fossils. Moreover, the remains of certain mollusks, such as the oysters, -are important rock builders. - -The phylum Mollusca has been divided into five classes: - -1. _Amphineura_—the chitons or sea-mice; shell composed of eight valves -or plates; not a common fossil. Ordovician to Recent. - -2. _Scaphopoda_—the tusk-shells; shell composed of a single tusk-like -valve; generally not a common fossil but locally abundant in certain -Cenozoic formations. Devonian to Recent. - -3. _Gastropoda_—the snails and slugs; slugs are without shells, snails -have a single-valved shell which is typically coiled; common fossils in -Paleozoic, Mesozoic, and Cenozoic rocks. Cambrian to Recent. - -4. _Pelecypoda_—clams, mussels, oysters, scallops; shells composed of -two valves, usually, but not always, of equal size; common fossils, -especially in Mesozoic and Cenozoic rocks. Cambrian to Recent. - -5. _Cephalopoda_—squids, octopuses, the pearly nautilus, and the -ammonoids (extinct); shell of one valve, usually coiled and partitioned -by septa; valuable fossils, especially in Paleozoic and Mesozoic rocks. -?Cambrian, Ordovician to Recent. - - [Illustration: Plate 18 - PENNSYLVANIAN BRACHIOPODS] - - MARGINIFERA × 1 - AMBOCOELIA × 1 - SQUAMULARIA × 1 - DERBYA × 1 - MESOLOBUS × 1 - CHONETES × 1 - LINOPRODUCTUS × 1 - PUNCTOSPIRIFER × 1 - COMPOSITA SUBTILITA × 1 - NEOSPIRIFER × 1 - - [Illustration: Plate 19 - PENNSYLVANIAN BRACHIOPODS] - - JURESANIA × 1 - SPIRIFER ROCKYMONTANUS × 1 - NEOSPIRIFER CAMERATUS × 1 - -Of these five classes, only the Gastropoda, Pelecypoda, and Cephalopoda -are discussed herein. - - CLASS GASTROPODA.— - -The typical gastropod has a spirally coiled, single-valved, unchambered -shell. This shell encloses a soft body possessing a well-defined head -with a pair of eyes and one or two pairs of tentacles. Most gastropods -have gills and live in shallow marine waters, but some inhabit fresh -water. Others are land-dwelling forms and breathe by means of lungs. - -Gastropod shells, both Recent and fossil, exhibit a great variety of -size, shape, and ornamentation. Such shells may be cone-shaped, spirally -coiled, flat, turreted, or cylindrical. The shell is commonly wound in a -spiral around a central axial pillar (the _columella_). The closed -pointed end of the shell is called the _apex_, and each turn of the -shell is called a _whorl_ (fig. 16). The last-formed and largest whorl -is called the _body whorl_, and this whorl contains the _aperture_—the -opening of the shell. The combined whorls exclusive of the body whorl -are known as the _spire_. The inner and outer margins of the aperture -are designated the _inner lip_ and the _outer lip_, respectively. In -some snails the aperture is closed by means of the _operculum_—a -calcareous or horny plate attached to the foot of the animal. This plate -effectively seals the aperture when the animal is withdrawn into its -shell. Some gastropods have shells that are loosely coiled, and in these -forms the columella is absent. If the whorls of such shells are not in -contact on the inner surface, this leaves an open space which is called -the _umbilicus_ (fig. 16a). The umbilicus is commonly seen as an opening -in the base of the gastropod shell, but in some forms the umbilical -opening may be partially or completely covered by a thick growth of -shell called the _callus_. - -Many gastropods, particularly those of the Texas Cretaceous, are -commonly preserved as internal or external molds. This type of -preservation occurs after the death of the animal, and the decomposition -of the soft parts enables the shell to become filled with sediment. This -filling later becomes solidified, and the outer shell may eventually be -removed by weathering or solution. This type of internal mold is called -a _steinkern_ and normally does not reflect any external shell -characteristics (Pl. 2). In some of the Pennsylvanian and Tertiary -formations, however, gastropods may be collected with the original shell -in an excellent state of preservation. - -Plates 20-23 illustrate some typical Paleozoic, Mesozoic, and Cenozoic -gastropods. - - CLASS PELECYPODA.— - -The pelecypods possess a shell composed of two calcareous valves (fig. -17) which enclose the soft parts of the animal. Members of this class -live exclusively in an aquatic habitat and are most abundant in marine -environments. Most pelecypods are slow-moving bottom-dwelling forms, but -some, like the oysters, are attached. Still others, for example, the -scallop or _Pecten_, are swimmers. The Pelecypoda include such familiar -saltwater forms as the clams and oysters, as well as the common -fresh-water mussel. Pelecypods range from Cambrian to Recent in age but -are more abundant in Mesozoic and Cenozoic rocks. - -The living animal is aquatic, with well-developed soft parts and a -muscular, commonly hatchet-shaped _foot_. The soft _mantle_ encloses the -body and secretes the shell, and in some pelecypods part of the mantle -is developed into the _incurrent_ and _excurrent_ siphons. The incurrent -siphons bring fresh water and food into the _mantle cavity_, and waste -products are passed out through the excurrent siphons. Respiration is by -means of gills within the mantle cavity. - -The typical pelecypod valves are of equal size and form, but some, such -as the scallops and oysters, have two valves of unequal size and shape. -The valves are hinged and held together by a tough elastic ligament -which runs along the _dorsal_ (top) side of the shell. In addition to -the ligament, most forms have _teeth_ and _sockets_ which are located -along the _hinge-line_. The teeth in one valve articulate with the -sockets in the opposite valve, and this arrangement gives strength to -the hinge. - - [Illustration: Fig. 16. Morphology and principal parts of gastropod - shells. (a) Low-spired form with umbilicus. (b) Section of spirally - coiled shell showing columella.] - - a - Suture - Whorl - Body whorl - Aperture - Umbilicus - b - Apex - Spire - Columella - Body whorl - Inner lip - Outer lip - -Most of the pelecypod shell is of calcium carbonate, but the outer -layer, or _periostracum_, of each valve is composed of horny material. -The inner surface of the shell is lined with a calcareous layer of -pearly or porcelaneous material. - - [Illustration: Plate 20 - PENNSYLVANIAN GASTROPODS] - - STRAPAROLUS × 1 - AMPHISCAPHA × 1 - WORTHENIA × 1 - TREPOSPIRA × 1 - BELLEROPHON × 1 - EUOMPHALUS × 1 - - [Illustration: Plate 21] - - [Illustration: PENNSYLVANIAN GASTROPODS] - - EUPHEMITES × 1 - STROBEUS × 1 - PLATYCERAS × 1 - - [Illustration: CRETACEOUS GASTROPODS - INTERNAL MOLDS] - - GYRODES × 1 - LUNATIA × 1 - TURRITELLA × 1 - CERITHIUM × 1 - TYLOSTOMA × 1 - NERINEA × 1 - - [Illustration: Plate 22 - TERTIARY GASTROPODS] - - DISTORSIO × 1 - MESALIA × 1 - FUSUS × 1 - COCHLESPIROPSIS × 1 - TURRITELLA × 1 - LATIRUS × 1 - CONUS × 1 - VERTAGUS × 1 - PSEUDOLIVA × 1 - - [Illustration: Plate 23 - TERTIARY GASTROPODS] - - ANCILLA × 1 - ARCHETECTONICA × 1 - TUBA × 1 - CALYPTRAPHORUS × 1 - SYCOSTOMA × 1 - SURCULA × 1 - VOLUTOLITHES × 1 - NEVERITA × 1 - LEVIFUSUS × 1 - -The outline of the shell may vary greatly, but most pelecypods are -typically clam-like. However, certain forms are round, others are long -and narrow, and some have wing-like structures. Most pelecypods have a -beak which represents the oldest part of the shell. The _beak_ is -commonly located on the _anterior_ (front) end of the shell, and the end -of the shell opposite this is designated _posterior_ (the rear). The -hinge and ligament are located dorsally (along the top), and the lower -margin of the shell where the valves open is called _ventral_ (fig. -17a). - - [Illustration: Fig. 17. Morphology and principal parts of a typical - pelecypod shell. (a) Exterior view. (b) Interior view.] - - a - Dorsal - Beak - Anterior - Posterior - Concentric growth rings - Ventral - b - Hinge teeth - Cardinal teeth - Anterior muscle scar - Posterior muscle scar - Mantle line - -The inner surface of the shell has certain markings which, along with -the shell form and dentition (the nature and arrangement of the teeth -and sockets), are important in classification. Muscle scars are present -on the inside of most valves; the _anterior muscle scars_ are located -near the front of the shell, and the _posterior muscle scars_ are -situated near the rear of the shell. These scars mark the place of -attachment of muscles which were used to close the shell and aid in -locomotion. Along the ventral margin of some shells there is a line or -scar which extends from the anterior muscle scar to the posterior muscle -scar. This is known as the _mantle line_ or _pallial line_ and marks the -place of attachment of the _mantle_—a soft membranous layer that -enclosed the body of the animal. In some pelecypods the dorsal margin of -one valve bears a series of _hinge teeth_ which articulate with a -similar set of sockets on the other valve (fig. 17b). In addition to -hinge teeth, certain species have _cardinal teeth_ which are located -below and in front of the hinge teeth. - -The exterior of most shells is marked by a series of _concentric growth -lines_ (fig. 17a) which mark points of periodic addition of shell -material. The external surface of many shells is also marked by various -types of ornamentation, such as ribs, nodes, spines, and grooves. - -Fossil collectors commonly find only one valve of the pelecypod shell. -This is because the shell normally opens when the animal dies, and the -valves may easily become separated. Fossil pelecypods are also commonly -preserved as external and internal molds, and these are found in -fossiliferous strata of almost all ages. Some pelecypods of -Pennsylvanian, Mesozoic, and Cenozoic age are found with original shell -material that appears to have undergone very little change. Fossil -pelecypods are abundant and varied in Texas and are found in most of the -fossiliferous formations of the Pennsylvanian, Cretaceous, and Tertiary -systems (Pls. 24-31). - - CLASS CEPHALOPODA.— - -These are marine mollusks with or without chambered or solid shells -which may be internal or external. The living animal possesses a -well-developed head with eyes, horny jaws, and many tentacles fused with -the foot. Cephalopods are the most advanced of all mollusks and include -the squid, octopus, pearly nautilus, and the extinct ammonoids. Members -of this class range from Cambrian to Recent in age but were much more -abundant in ancient seas than they are today. Their remains constitute a -very useful group of fossils, particularly in Paleozoic and Mesozoic -rocks. - -Most paleontologists have divided the Cephalopoda into three subclasses, -the Nautiloidea, Ammonoidea, and the Coleoidea (known also as subclass -Dibranchiata and subclass Decapoda); each of these is discussed below. - - Subclass Nautiloidea.— - -The nautiloids are cephalopods with external chambered shells in which -the _septa_ (dividing partitions) are simple and have smooth edges. This -subclass is represented by a single living genus, _Nautilus_, and a -large number of fossil forms. - -In the living _Nautilus_ the shell is composed of calcium carbonate and -is coiled in a flat spiral (fig. 18). The interior of the shell is -divided into a series of _chambers_ by calcareous partitions called -_septa_. The point where each septum joins the inner surface of the -shell is known as the _suture_. These _suture lines_ (fig. 19a) are not -visible from the outside unless the outer shell has been removed, but -they are visible on the internal molds of many fossil cephalopods and -are of great importance in nautiloid and ammonoid classification. -Nautiloids have very simple smoothly curved suture patterns, but -ammonoids are characterized by more complex and wrinkled sutures (fig. -19d). - -Although the shell of the only type of living nautiloid is coiled, many -of the early forms had straight cone-shaped shells (_Orthoceras_, Pl. -32), and these are common in some of the Pennsylvanian formations of -Texas. Fossil coiled nautiloids may be collected in certain of the -Cretaceous and Tertiary strata of the State, but their remains are not -common. _Cymatoceras_ (Pl. 32) is a coiled fossil nautiloid from the -Cretaceous of north Texas. - - [Illustration: Plate 24 - PENNSYLVANIAN PELECYPODS] - - SCHIZODUS × 1 - MYALINA × ½ - ASTARTELLA × 1 - NUCULOPSIS × 1 - ALLORISMA × 1 - NUCULANA × 1 - YOLDIA × 1 - PINNA × ½ - - [Illustration: Plate 25 - CRETACEOUS PELECYPODS] - - PROTOCARDIA × 1 - ALECTRYONIA LUGUBRIS × 1 - PLICATULA × 1 - PECTEN × 1 - - [Illustration: Plate 26 - CRETACEOUS PELECYPODS] - - GRYPHAEA WASHITAENSIS × 1 - GRYPHAEA GRAYSONANA × 1 - INOCERAMUS × 1 - TRIGONIA × 1 - - [Illustration: Plate 27 - CRETACEOUS PELECYPODS] - - EXOGYRA ARIETINA × 1 - EXOGYRA LAEVISCULA × 1 - NEITHEA × 1 - EXOGYRA PONDEROSA × 1 - EXOGYRA TEXANA × 1 - - [Illustration: Plate 28 - CRETACEOUS PELECYPODS] - - PACHYMYA × ½ - OSTREA CARINATA × 1 - OSTREA QUADRIPLICATA × 1 - PHOLADOMYA × 1 - - [Illustration: Plate 29 - TERTIARY PELECYPODS] - - LIMA × 1 - OSTREA LISBONENSIS × 1 - PITAR × 1 - VENERICARDIA BULLA × 1 - PACHECOA × 2 - PHOLADOMYA × 2 - OSTREA SELLAEFORMIS × 1 - CRASSATELLA × 1 - - [Illustration: Plate 30 - TERTIARY PELECYPODS] - - ORTHOYOLDIA × 1 - TELLINA × 1 - VOKESULA × 2 - NUCULA × 2 - VENERICARDIA × ½ - - [Illustration: Plate 31 - TERTIARY PELECYPODS] - - PLICATULA × 1 - PECTEN × 1 - ANOMIA × 1 - GLYCYMERIS × 2 - CARYOCORBULA × 2 - BARBATIA × 1 - - [Illustration: Fig. 18. Morphology and principal parts of the pearly -nautilus. (a) Exterior view of a Recent shell. (b) Sectioned view of the - same shell to show internal structures.] - - b - Living chamber - Aperture - Septa - Siphuncle - Protoconch - Chamber - -[Illustration: Fig. 19. Characteristic features of the various types of - cephalopod sutures. (a) Nautiloid type. (b) Goniatite type. (c) - Ceratite type. (d) Ammonite type.] - - Subclass Ammonoidea.— - -The ammonoids are a group of extinct cephalopods which are related to -the nautiloids but are characterized by more complex suture patterns. -Members of this subclass have an external partitioned shell which is -straight, curved, or spirally coiled (Pl. 33). This group of cephalopods -first appeared in Devonian time, became extremely abundant and varied -during the Mesozoic, and was extinct by the end of the Cretaceous -period. - -Most Paleozoic ammonoids are characterized by a combination curved and -angular suture pattern, and this type of suture pattern is referred to -as _goniatitic_ (fig. 19b). Sutures that are curved and crenulated -(marked in places by a series of tooth-like indentations) are known as -_ceratitic_ (fig. 19c). Ceratitic sutures first appeared in the -Mississippian, became increasingly abundant during the Triassic but were -much less abundant during the Cretaceous. The _ammonitic_ suture has a -very complexly subdivided pattern (fig. 19d). Cephalopods with ammonitic -sutures range from Pennsylvanian to Cretaceous in age and were the most -abundant cephalopods of the Mesozoic. - - [Illustration: Plate 32] - - [Illustration: PENNSYLVANIAN CEPHALOPODS] - - PHANEROCERAS × 1 - ORTHOCERAS × 1 - - [Illustration: CRETACEOUS CEPHALOPODS] - - METOICOCERAS × ½ - CYMATOCERAS × ½ - - [Illustration: Plate 33 - CRETACEOUS CEPHALOPODS] - - TEXANITES × ½ - ACANTHOCERAS × ½ - TURRILITES × ½ - DUFRENOYIA × ½ - OXYTROPIDOCERAS × ½ - BACULITES × ½ - BELEMNITE × ½ - -Ammonoids are locally abundant in many of the fossiliferous rocks of -Texas and are among the more useful Mesozoic guide fossils. Goniatites -may be found in the Pennsylvanian of north-central and Trans-Pecos -Texas, and ammonoids with the ceratitic suture pattern can be collected -from the Lower Cretaceous of many parts of the State. Cephalopods -exhibiting the typical ammonitic suture pattern are abundant in many of -the Cretaceous rocks of Texas, and these fossils have contributed much -toward an understanding of the Cretaceous strata of this State. - - Subclass Coleoidea.— - -These are squid-like cephalopods characterized by an internal shell or -no shell at all. Included in this group are the squids, cuttlefish, -octopuses, and the extinct belemnoids, but of these only the belemnoids -are useful fossils. Members of this subclass range from Mississippian to -Recent in age. - - Order Belemnoidea.— - -The belemnoids appear to be the oldest and most primitive of the coleoid -cephalopods. Their earliest known occurrence is in rocks of -Mississippian age, and they were particularly abundant during the -Mesozoic. They became extinct at the end of Cretaceous time but have -left considerable evidence of their existence in the Mesozoic strata of -many parts of the world. Certain forms, because of their abundance and -relatively short geologic range, are excellent guide fossils. Belemnoids -have been found in the Upper Cretaceous of Texas (Pl. 33) but in general -are rare or unknown in most Texas formations. - - - Phylum Annelida - -Members of the phylum Annelida include the segmented worms such as the -common earthworm. Annelids are marine, fresh water, or terrestrial and -have apparently been common through much of geologic time. Because of -their lack of hard parts, most of these worms have left little direct -fossil evidence of their activities in the geologic past. Some annelids -secrete straight or coiled calcareous tubes, and fossil worm tubes of -this sort (fig. 20) are commonly found attached to brachiopods, -mollusks, and other objects. Tubes of this nature have been reported -from Paleozoic, Mesozoic, and Cenozoic rocks in Texas. - - [Illustration: Fig. 20. Types of typical annelid worms. (a) _Serpula_ - (×1) (b) _Hamulus_ (×2). (c) _Spirobis_ (×15).] - -Some annelids have small chitinous jaws and teeth which also may be -preserved as fossils. These dental structures are called scolecodonts -and are microfossils. - - - Phylum Arthropoda - -The arthropods are one of the more advanced groups of invertebrates, and -they are known from the Cambrian to the Recent (Pl. 34). Modern -representatives of this group include the crabs, shrimp, crayfish, -insects, and spiders. Arthropods vary greatly in size and shape and are -among the most abundant of all animals. They have become successfully -adapted to a wide variety of environments and live on land, in water, -and in the air. The typical arthropod has a segmented body which is -usually covered by a chitinous exoskeleton which, in some forms, -contains additions of calcium carbonate. They are highly specialized and -well-developed animals in which locomotion is by means of paired jointed -appendages. - -Although the arthropods are of great importance in nature today, only a -few groups are of importance to the paleontologist. Only two of these, -the trilobites and the ostracodes, are discussed herein. - - - Subphylum Trilobitomorpha - -The members of this subphylum are extinct arthropods which were most -abundant during early Paleozoic time. - - CLASS TRILOBITA.— - -The trilobites are a group of exclusively marine arthropods which derive -their name from the typical three-lobed appearance of their bodies (fig. -21a). The trilobite body is divided into a _central_ or _axial_ lobe and -two _lateral_ lobes. The body of the animal was encased in a chitinous -exoskeleton. The top part of this exterior covering, the _carapace_, is -very thick, and it is this part of the trilobite that is usually -preserved. - - [Illustration: Plate 34 - FOSSIL ARTHROPODS] - - FOSSIL INSECT × 1 - FOSSIL CRUSTACEANS - ENOPLOCLYTIA × 1⅓ - ASTACODES × ¾ - NOTOPOCORYSTES × 2 - OSTRACODES × 40 - - [Illustration: Fig. 21. Morphology and principal parts of trilobites.] - - Cephalon - Thorax - Pygidium - Axial lobe - Lateral lobes - -The body is also divided into three parts from front to back. Beginning -at the front of the animal these divisions are the _cephalon_ or head, -the _thorax_ or abdomen, and the _pygidium_ or tail (fig. 21a). The body -segments of the thorax were arranged in such a manner as to permit the -animal to roll up into a ball, and many trilobites are found in this -position (fig. 21b). - -Trilobites first appeared in the Cambrian and were extinct by the end of -the Permian. They occur sparingly in certain of the Paleozoic rocks of -Texas and when found are likely to be fragmental and in a poor state of -preservation. - - - Subphylum Crustacea - -The crustaceans are the crabs, shrimp, crayfish, and ostracodes. -Although not abundant, fossil crabs have been described from certain -Cretaceous and Tertiary formations of the State (_Notopocorystes_, Pl. -34). However, the most useful and abundant crustacean fossils are the -members of the class Ostracoda. - - CLASS OSTRACODA.— - -The ostracodes are small, bivalved, aquatic crustaceans which have the -external appearance of small clams (Pl. 34). The remains of these tiny -animals are so small that they are best studied under a low-power -microscope, and because of their small size they are particularly useful -to the micropaleontologist. - -Fossil ostracodes range from Ordovician to Recent in age and have been -recorded in the Paleozoic, Mesozoic, and Cenozoic rocks of Texas. Their -remains are particularly abundant in certain of the Cretaceous and -Tertiary marine formations of the State. - - - Phylum Echinodermata - -The echinoderms are a large group of exclusively marine animals, most of -which exhibit a marked five-fold radial symmetry (Pls. 35, 36). Living -echinoderms have well-developed nervous and digestive systems, a -distinct body cavity, and are a relatively complex group of organisms. - -The typical echinoderm has a skeleton composed of numerous calcareous -plates which are intricately fitted together and covered by a leathery -outer skin (the _integument_). The echinoderm body often exhibits a -typical star-shaped form, but some types may be heart-shaped, -biscuit-shaped, or cucumber-shaped. - -Members of this phylum range from Cambrian to Recent in age and are -abundant as fossils in many of the marine formations of Texas. - -The phylum Echinodermata has been divided into two subphyla, the -Pelmatozoa (those forms that were attached to sea floor by a stem or a -stalk) and the Eleutherozoa (the stemless unattached echinoderms). - - - Subphylum Pelmatozoa - -These are echinoderms which are more or less permanently attached to the -bottom of the sea by means of a stalk which is composed of slightly -movable, calcareous, disk-like segments (fig. 23). - -Pelmatozoans range from Cambrian to Recent in age, and their fossilized -remains are particularly abundant in Paleozoic rocks. The subphylum has -been divided into several classes, but only three of these, the -Cystoidea, Blastoidea, and Crinoidea, are discussed here. With the -exception of the Crinoidea, all of the attached echinoderms are extinct. - - CLASS CYSTOIDEA.— - -These are primitive attached echinoderms which were relatively common in -early Paleozoic time. The typical cystoid has a somewhat globular or -sac-like _calyx_ (the main body skeleton) composed of numerous, -irregularly arranged, calcareous plates (fig. 22b). The plates composing -the calyx are usually perforated by pores or slits which were probably -used in excretion or respiration. The calyx was attached to the sea -bottom by a short stem. - -Cystoids range from Cambrian to Devonian in age and were especially -abundant during Ordovician and Silurian time. Their remains are rare or -absent in the rocks of Texas. - - [Illustration: Fig. 22. Two extinct attached echinoderms. (a) - _Pentremites_ (Mississippian). (b) _Caryocrinites_ (Silurian).] - - CLASS BLASTOIDEA.— - -The blastoids are extinct short-stemmed echinoderms with a small, -symmetrical, bud-like calyx. The blastoid calyx is composed of 13 -calcareous plates arranged in a typical five-sided pattern (fig. 22a). -The _mouth_ is located in the center of the calyx and is surrounded by -five openings called _spiracles_. Five distinct _ambulacral_ or _food -grooves_ radiate outward from the mouth. - -Blastoids range from Ordovician to Permian in age and were especially -abundant during the Mississippian period. No blastoids have been -reported from any of the rocks of Texas. - - CLASS CRINOIDEA.— - -The crinoids are commonly called _sea-lilies_ because of their -flower-like appearance. The _calyx_ is composed of symmetrically -arranged calcareous plates, and most crinoids have a long stem. Other -crinoids are free-swimming in the adult stage and are attached only -during the earlier phases of their development. - -The crinoid calyx is typically cup-shaped (fig. 23) and five grooves -radiate out from its center. These grooves continue outward along the -complexly segmented arms and are used as channels to convey food to the -mouth. - - [Illustration: Fig. 23. Typical modern crinoid, or “sea lily,” showing - principal parts.] - - Calyx - Arm - Plate - Stem - Columnal - Cirri - Holdfast (root) - -The crinoid stem is attached to the base of the calyx and serves for -purposes of support and attachment. This stem consists of a relatively -long flexible stalk composed of numerous calcareous disk-shaped segments -called _columnals_ (fig. 23; Pl. 35), each of which contains a round or -star-shaped opening in its center. Many crinoids have very long stalks -(some are as much as 50 feet in length), and when the animal dies the -columnals become separated and are scattered about on the ocean floor. -Many Paleozoic limestones contain such great numbers of crinoid -columnals that they are referred to as _crinoidal limestones_ (fig. 8). -Crinoidal limestones occur in some of the Mississippian and -Pennsylvanian formations of central Texas and in the Pennsylvanian of -north-central and Trans-Pecos Texas. - -The stalk is attached to the sea floor or some other object by means of -a root system called the _holdfast_ (fig. 23). This structure commonly -branches out into the surrounding sediments, and in this manner the -crinoid animal is firmly anchored to the bottom of the sea. - -Crinoids, like most echinoderms, are gregarious animals—that is, they -commonly live together in large numbers, and for this reason great -numbers of crinoid remains are commonly found concentrated in relatively -small local areas. Most fossil crinoids are found as stem fragments -because the more fragile calyx and root system are less likely to be -preserved. - -The earliest known crinoids have been found in rocks of Ordovician age, -and their remains are particularly abundant in Paleozoic rocks. Crinoids -are living today but most of them are stemless free-swimming forms -called “feather stars,” much less abundant than their Paleozoic -ancestors. - - - Subphylum Eleutherozoa - -The eleutherozoans are free-swimming, bottom-dwelling, echinoderms which -have been divided into two classes. The class Asterozoa (star-shaped -echinoderms) contains the subclasses Asteroidea (the starfishes) and the -Ophiuroidea (the brittle stars). Although they are known as fossils, -neither of these groups is of paleontological importance. The class -Echinozoa (echinoderms without laterally directed arm-like extensions) -contains the subclasses Echinoidea (the sea urchins and sand dollars) -and Holothuroidea (the sea cucumbers). Of these two subclasses, only the -Echinoidea are useful fossils. - - CLASS ASTEROZOA.— - -These are typical star-shaped free-moving echinoderms in which the body -is divided into a central disk and radiating arms. - - Subclass Asteroidea.— - -This class contains the starfishes which, although not common fossils, -illustrate well the typical echinoderm characteristics (Pl. 35). Fossil -starfishes have been found sparingly in certain formations in Texas, but -well-preserved specimens are quite rare. However, excellently preserved -starfishes have been found in slabs of Cretaceous limestones from -central and north-central Texas. - - Subclass Ophiuroidea.— - -The ophiuroids are echinoderms with a well-defined central disk and five -long, slender, whip-like arms. They have been called brittle stars -because of their ability to shed their arms when they are disturbed. -Their long, slender, snake-like arms have also resulted in their being -called serpent stars. Ophiuroids range from Ordovician to Recent in age, -but because of the delicate nature of their bodies they are seldom found -as fossils. Ophiuroid remains have been found in certain Mesozoic and -Cenozoic rocks of Texas, but they consist largely of small segments of -the arms or body fragments. - - CLASS ECHINOZOA.— - -The echinozoans are a group of unattached echinoderms whose bodies -consist of numerous calcareous plates and spines, but they do not -possess the radiating arm-like extensions which characterize the -asterozoans. - - Subclass Echinoidea.— - -Echinoids are free-moving echinoderms with disk-shaped, heart-shaped, -biscuit-shaped, or globular exoskeletons (Pl. 36). Modern -representatives of this group include the familiar sea urchins, heart -urchins, and the sand dollars. - - [Illustration: Plate 35] - - CRINOIDS - CRINOID CALYX × ½ - CRINOID COLUMNALS × 1 - HOLOTHURIAN SCLERITES (GREATLY ENLARGED) - CRETACEOUS FOSSIL STARFISHES - PENTAGONASTER × 1 - PENTACEROS × 1 - - [Illustration: Plate 36 - CRETACEOUS ECHINOIDS] - - SALENIA × 1 - ECHINOID SPINES × 2 - ECHINOID PLATE × 2 - HEMIASTER × 1 - HOLASTER × 1 - HOLECTYPUS × 1 - -The echinoid _test_ (exoskeleton) is composed of many intricately -fitting calcareous plates (Pl. 36) which enclose the animal’s soft -parts. The exterior of the test is typically covered with large numbers -of movable spines (Pl. 36) which vary greatly in size. These spines are -of some aid in locomotion, support the skeleton of the animal, and -provide a measure of protection from enemies. - -The oldest known echinoids have been recorded from rocks of Ordovician -age, but it was not until the Mesozoic that the group began to flourish. -They were especially abundant during the Cretaceous and have been -abundant and varied from that time until the present. - -Echinoids are particularly numerous in many of the Lower Cretaceous -formations of Texas where they are commonly found in an excellent state -of preservation. Heart urchins and biscuit urchins may be found in large -numbers in many areas of the State, and especially in areas where there -are good exposures of fossiliferous Lower Cretaceous rocks. - - Subclass Holothuroidea.— - -Members of this class, commonly called _sea cucumbers_, have a rather -elongate, sac-like, cucumber-shaped body and bear little resemblance to -other members of the phylum Echinodermata. The sea cucumbers do not have -a well-defined skeleton; rather the body is supported by many small, -disconnected, calcareous plates or rods called _ossicles_ or _sclerites_ -(Pl. 35). These minute structures are embedded in the leathery skin -which covers the body of the sea cucumber and may be preserved as -fossils. Such remains are locally abundant in certain formations in -Texas, but because of their small size, scattered occurrence, and -problems in classification, this group is of little use to most -paleontologists. - -Holothuroid body impressions have been reported from the Middle -Cambrian, and sclerites from rocks as old as Mississippian. - - - Phylum Chordata - -The chordates are the most advanced of all animals and are characterized -by the presence of a well-developed nervous system and a body supported -by a bony or cartilaginous _notochord_ and/or _spinal column_. In the -higher chordates (the vertebrates) the notochord is normally replaced by -bone, but in the lower chordates (for example, the graptolites) it -remains in a cartilaginous condition. - -The phylum Chordata contains only two subphyla of paleontological -significance. These are the subphylum Hemichordata, composed of -primitive chordates (including the graptolites which are important -fossils), and the Vertebrata, which includes all animals with backbones. - - - Subphylum Hemichordata - -The hemichordates are characterized by a well-defined notochord which -runs the length of the body, but they do not possess a true backbone. -Only one class, the Graptolithina, is of paleontological importance. - - CLASS GRAPTOLITHINA.— - -The graptolites are a group of extinct colonial animals which were very -abundant during early Paleozoic time. They are characterized by a -chitinous exoskeleton consisting of rows of cups or tubes which housed -the living animal. These cups are attached to single or branching stalks -(fig. 24) which in some forms were attached to sea weeds, rocks, or -other foreign objects where they led a fixed existence. The stalks of -the unattached graptolites grew on floats (fig. 24a) and these floating -forms attained wide geographic distribution. It is also possible that -some of the attached forms were fixed to floating objects, such as sea -weed, and thus were distributed in this manner. - -Previous classifications have recognized the graptolites as members of -the phylum Coelenterata. As coelenterates they were assigned, at various -times, to the classes Hydrozoa, Scyphozoa, and Graptozoa. In addition, -they were also classified as bryozoans by certain of the early -paleontologists. This publication, in keeping with recent changes in -taxonomy, considers graptolites to be an extinct group of hemichordates. -This classification is based upon research in which uncompressed -graptolites were etched out of chert and studied in great detail. -Information derived from these relatively undistorted specimens -indicates a much higher degree of body organization than was previously -suspected, and as a result of these studies most paleontologists now -consider graptolites to be some form of primitive chordate. - - [Illustration: Fig. 24. Graptolites. (a) Diplograptus (×2). (b) - Dendrograptus (×3). (c) Phyllograptus (×2).] - -The chitinous graptolite exoskeleton is commonly preserved as a -flattened carbon residue; their remains may be locally abundant along -the bedding planes of certain black or dark gray shales. - -Graptolites are known from rocks that range from Cambrian to -Mississippian in age, and they are among the most important guide -fossils for Ordovician and Silurian rocks. - -Graptolites have been reported from Cambrian rocks in central Texas and -from the Ordovician of west Texas (fig. 24). The most abundant of these -occur in certain Ordovician rocks in the Trans-Pecos area where they are -common fossils in certain formations. - - - Subphylum Vertebrata - -The vertebrates are the most advanced of all chordates. They are -characterized by a skull and a bony or cartilaginous _internal -skeleton_, with a _vertebral column_ of bone or cartilage. This -subphylum is commonly divided into two superclasses, the Pisces (the -fishes and their relatives) and the Tetrapoda (the four-footed animals). - -As mentioned earlier, most amateur collectors collect very few -vertebrate remains, and for this reason this group is not discussed in -detail. However, the more important vertebrate classes are briefly -reviewed to enable the reader to have some understanding of this -important group of animals. This part of the handbook will also serve as -an introduction to some of the interesting and unusual, but now extinct, -animals that have inhabited Texas in the geologic past. Among these -animals are giant fishes, primitive amphibians, and many different types -of dinosaurs. Included also are such unusual mammals as the giant ground -sloths, saber-tooth cats, mammoths, and mastodons, all of which are now -extinct. The remains of these, and many other interesting extinct -vertebrates, may be seen in the geological collections of the Texas -Memorial Museum at Austin. Many of these displays are accompanied by -drawings which depict the scientific restoration of the animal’s soft -parts and show how the animal may have appeared in life. - - Superclass Pisces - -The members of this superclass are commonly called fishes and are the -simplest and most numerous of all vertebrates. They are aquatic, -free-moving, cold-blooded (their blood maintains the temperature of the -surrounding water), and breathe primarily by means of gills. However, -some forms (the lungfishes) breathe by means of a lung developed from -the air-bladder. - -The most recent fish classification recognizes four major classes, the -Agnatha (primitive jawless fishes), the Placodermi (armored fishes with -primitive jaws), the Chondrichthyes (sharks and related forms with -cartilaginous internal skeletons), and the Osteichthyes (true bony -fishes). - - CLASS AGNATHA.— - -Fishes belonging to this class are primitive, jawless, and represented -by the living lampreys and hagfishes. The first agnathans appeared in -the Ordovician and were armored by a bony covering on the front part of -their bodies. These primitive fishes, called _ostracoderms_, are the -earliest recorded fishes and, in addition, appear to be the first known -vertebrate animals. The ostracoderms first appeared in late Ordovician -time, increased in numbers in the Silurian, and were extinct by the end -of the Devonian. - - CLASS PLACODERMI.— - -These are primitive jaw-bearing fishes, the majority of which were -heavily armored (Pl. 37). The _placoderms_ were shark-like in -appearance, and some of them grew to be as much as 30 feet in length. -Members of this class appeared first in the Devonian and lasted into the -Permian, at which time they became extinct. Placoderms are rare in -Texas, but the fragmentary remains of these primitive fishes have been -found in Devonian rocks in central Texas. - - CLASS CHONDRICHTHYES.— - -This class includes such modern forms as the sharks, rays, and skates. -They are characterized by skeletons which are composed of cartilage and -are very abundant in the marine waters of today. The earliest known -representatives of this class are reported from rocks of Devonian age, -and they have been relatively common up to the present time. - -Shark teeth (Pl. 37) can be found in Texas in Pennsylvanian, Permian, -Cretaceous, Paleocene, Eocene, and Miocene rocks. These are probably the -most common vertebrate fossils to be found in Texas and are usually -found in thin-bedded marine limestones or clays. - - CLASS OSTEICHTHYES.— - -The Osteichthyes includes the true bony fishes, which are the most -highly developed and abundant of all fishes. They possess an internal -bony skeleton, well-developed jaws, an air-bladder, and, typically, an -external covering of overlapping scales. - -Included in this class are a primitive group of fishes called -_crossopterygians_. These were very abundant in the Devonian and are -believed to be the ancestors of the amphibians. The modern lungfishes -also belong to the class Osteichthyes, and these primitive fishes, which -are now found only in Australia, South America, and Africa, breathe by -means of gills and lungs which have been developed from the air-bladder. -Although not abundant as fossils, the remains of these specialized -fishes have added much to present knowledge concerning the development -of certain of the higher vertebrates. - -The remains of bony fishes have been collected at many localities in -Texas, and fossils of this type have been found primarily in rocks of -Cretaceous age but have been reported from other rocks as well. Fish -fossils are more commonly found in the form of teeth (Pl. 37), -vertebrae, scales, and an occasional well-preserved skeleton. - - [Illustration: Plate 37] - - [Illustration: SHARK TEETH × 1] - - [Illustration: CONODONTS - (GREATLY ENLARGED)] - - [Illustration: PRIMITIVE ARMORED FISH - PLACODERM (DEVONIAN) - × ½] - -_Conodonts_ (Pl. 37) are small, amber-colored, tooth-like fossils which -are believed to represent the teeth of some type of extinct fish. -Although geologists do not know a great deal about the origin of these -strange fossils they are of value in micropaleontology. Conodonts have -been reported from several Paleozoic formations in Texas and are useful -guide fossils in some areas. - - Superclass Tetrapoda - -The tetrapods are the most advanced chordates and are typified by the -presence of lungs, a three- or four-chambered heart, and paired -appendages. Included here are the classes Amphibia (frogs, toads, and -salamanders), Reptilia (lizards, snakes, turtles, and the extinct -dinosaurs), Aves (birds), and Mammalia (including the mammals, such as -men, dogs, whales, etc.). - - CLASS AMPHIBIA.— - -The amphibians were the earliest developed four-legged animals and are -represented by such living forms as the toads, frogs, and salamanders. -Amphibians are cold-blooded animals that primarily breathe by lungs and -spend most of their life on land, but during their early stages of -development they live in the water where they breathe by means of gills. - -The amphibians apparently developed from the crossopterygian fishes -during late Devonian time and were relatively abundant in the -Pennsylvanian, Permian, and Triassic. - -Amphibian remains in Texas are confined largely to lower Paleozoic and -upper Mesozoic rocks. Numerous interesting and important discoveries of -fossil amphibians have been made in north and west Texas where their -remains (Pl. 40) have been collected in association with early types of -reptiles. The areas where Permian red beds are exposed in Archer and -Baylor counties and where Triassic red beds are exposed from Big Spring -north along the edge of the High Plains have furnished most of these -specimens. - - CLASS REPTILIA.— - -The reptiles have become adapted to permanent life on land and need not -rely on an aquatic environment. They are cold-blooded and are normally -characterized by a scaly skin. Reptiles have been much more abundant in -the past than they are today, and they assumed many different shapes and -sizes in the geologic past. Modern classifications recognize a large -number of reptilian groups, but only the more important of these are -briefly reviewed here. - - Cotylosaurs.— - -These were a group of primitive reptiles which, although retaining some -amphibian characteristics, became adapted to an exclusively -land-dwelling existence. The cotylosaurs lived during the Pennsylvanian -and Permian and apparently became extinct sometime during the late -Permian. Cotylosaurs (Pl. 40) are well known from the Permian of north -Texas. - - Turtles.— - -These are reptiles in which the body is more or less completely enclosed -by bony plates. This group is first known as fossils from late Triassic -rocks of Europe, and modern representatives of the group include the -turtles and tortoises. Fragmentary remains of turtle shells are among -the most common vertebrate fossils found in the Tertiary. Some of the -late Tertiary land tortoises were 3 to 4 feet long. The earliest known -turtles in Texas have been found in Cretaceous rocks. - - Pelycosaurs.— - -The pelycosaurs were a group of late Paleozoic reptiles some of which -were characterized by the presence of a tall fin on their back (Pl. 40). -The fossils of these unusual creatures are well known from the Permian -red beds of north-central Texas. - - Therapsids.— - -The therapsids were a mammal-like group of reptiles which were well -developed for a terrestrial existence. Although the remains of these -primitive reptiles are not particularly important fossils, study of the -therapsids has provided much valuable information about the origin of -the mammals. Members of this group appeared first in the middle Permian -and persisted until the middle Jurassic, but therapsid remains have not -been reported from Texas. - - [Illustration: Plate 38 - Comparison of the dinosaurs. Reproduced with permission of Dr. J. W. - Dixon, Jr., and Geology Department, Baylor University, Waco, Texas.] - - DINOSAUR SAURISCHIANS ORNITHISCHIANS - STOCKS - - DINOSAUR THEROPOD SAUROPOD ORNITHOPOD STEGOSAUR CERATOPSIAN ANKYLOSAUR - TYPES - POSTURE BIPEDAL QUADRUPEDAL BIPEDAL AND QUADRUPEDAL QUADRUPEDAL QUADRUPEDAL - QUADRUPEDAL - ARMOR UNARMORED EXCEPT UNARMORED UNARMORED (SPEED BONY PLATES HORNS, BONY KNOBS AND SPIKES - FOR HUGE SHARP WAS CHIEF ALONG BACK, PLATE OVER NECK OVER DORSAL AREA, - TEETH DEFENSE) SPIKED-TAIL CLUB-LIKE TAIL - DIET CARNIVOROUS HERBIVOROUS HERBIVOROUS HERBIVOROUS HERBIVOROUS HERBIVOROUS - OTHER LARGE HEAD WITH HUGE BODY, LONG SLENDER-BUILD, SHORT NECK, SHORT NECK, “ARMADILLO-LIKE” - DESCRIPTIVE POWERFUL JAW, NECK AND TAIL, “DUCK-BILLED” LONG TAIL, STOCKY BUILD APPEARANCE - REMARKS GREATLY REDUCED SMALL HEAD SMALL HEAD - FORE-LIMBS - EXAMPLES CERATOSAURUS-J BRACHIOSAURUS-J PARASAUROLOPHUS-K _STEGOSAURUS-J_ STYRACOSAURUS-K PALEOSCINCUS-K - (AND AGE) ALLOSAURUS-J DIPLODOCUS-J CORYTHOSAURUS-K PROTOCERATOPS-K _ANKYLOSAURUS-K_ - J-JURASSIC _TYRANNOSAURUS-K_ _BRONTOSAURUS-J_ _TRACHODON-K_ _TRICERATOPS-K_ - K-CRETACEOUS - [Illustration] [Illustration] [Illustration] [Illustration] [Illustration] [Illustration] - SCALE IN FEET 10 10 5 5 5 5 - - [Illustration: Plate 39 - Comparison of Mesozoic flying and swimming reptiles. Reproduced with - permission of Dr. J. W. Dixon, Jr., and Geology Department, Baylor - University, Waco, Texas.] - - [Illustration: FLYING REPTILES—PTEROSAURS] - - GROUP AGE TEETH TAIL HEAD SIZE EXAMPLE - - RHAMPHORHYNCHOIDS JURASSIC WELL LONG TAIL WITHOUT SMALL [Illustration] - DEVELOPED WITH CREST MAXIMUM _RHAMPHORHYNCHUS_ - FLATTENED WINGSPAN - RUDDER AT OF 2 FEET - END - PTERODACTYLOIDS JURASSIC JAW PARTLY SHORT OR WITH SMALL FROM SIZE [Illustration] - AND OR NO TAIL OR LARGE OF _PTERANODON-K_ - CRETACEOUS COMPLETELY CREST SPARROW - TOOTHLESS, TO GIANTS - HORNEY BEAK WITH SPAN - OF 25′ - - [Illustration: MESOZOIC SWIMMING REPTILES] - - GROUP AGE DESCRIPTION SIZE HABITAT EXAMPLE - - ICHTHYOSAUR TRIASSIC FISH-LIKE BODY, AVERAGE MARINE [Illustration] - TO HEAD LONG AND LENGTH = _ICHTHYOSAURUS-J_ - CRETACEOUS POINTED, NO 7′ - DISTINCT NECK MAXIMUM - LENGTH = - 43′ - MOSASAUR CRETACEOUS LIZARD-LIKE AVERAGE MARINE [Illustration] - BODY, FLATTENED LENGTH = _PYLOSAURUS_ - TAIL, 15′-20′ - DOUBLE-JOINTED MAXIMUM - JAW, RECURVED LENGTH = - TEETH 50′ - PLESIOSAUR TRIASSIC LONG NECK AND MAXIMUM MARINE [Illustration] - TO SMALL HEAD OR LENGTH = _ELASMOSAURUS-K_ - CRETACEOUS LONG HEAD AND 50′ _TRINACROMERUM-K_ - SHORT NECK, - POWERFUL FLIPPERS - CHELONIA TRIASSIC SHAPED LIKE MAXIMUM MARINE, [Illustration] - (TURTLES) TO PRESENT MODERN TURTLES, SIZE = STREAMS, _ARCHELON-K_ - BODY COVERED 11′ × 12′ AND - WITH BONY PLATES TERRESTRIAL - PHYTOSAUR TRIASSIC CROCODILE-LIKE MAXIMUM STREAMS [Illustration] - BODY, NOSTRILS LENGTH = AND SWAMPS _RUTIODON_ - ON A “HUMP” 25′ - ALMOST BETWEEN - THE EYES - - [Illustration: Plate 40] - - PELYCOSAUR × ¹/₁₂ - DIMETRODON - PRIMITIVE AMPHIBIAN × ¹/₂₀ - ERYOPS - COTYLOSAUR - SEYMOURIA × ⅕ - - [Illustration: Plate 41 - SWIMMING REPTILES] - - ICHTHYOSAUR × ¹/₁₂₀ - MOSASAUR × ¹/₆₀ - PLESIOSAUR × ¹/₆₀ - - [Illustration: Plate 42] - - [Illustration: CROCODILE-LIKE REPTILE - × ¹/₅₀ - PHYTOSAUR] - - [Illustration: FLYING DINOSAURS] - - RHAMPHORHYNCHUS × ⅙ - PTERANODON × ¹/₄₀ - - Ichthyosaurs.— - -These were extinct, short-necked, marine reptiles that were fish-like in -appearance. Ichthyosaurs resemble the modern dolphins, and some of them -attained lengths of 25 to 40 feet (Pl. 41), though the average was much -less. The group is known from rocks ranging from middle Triassic to late -Cretaceous in age. - - Mosasaurs.— - -The mosasaurs are another group of extinct marine lizards which lived in -Cretaceous seas. Some of these great reptiles grew to be as much as 50 -feet long, and their great gaping jaws were filled with many sharp -recurved teeth (Pl. 41). Mosasaurs were present in the great Cretaceous -seas which covered many parts of Texas, and their remains have been -reported from both north and central Texas. One such skeleton was found -near Austin, and its skull is on display in the Texas Memorial Museum. - - Plesiosaurs.— - -The plesiosaurs were marine reptiles which were characterized by a broad -turtle-like body, paddle-like flippers, and a long neck and tail (Pl. -41). These reptiles were not as streamlined or well equipped for -swimming as the ichthyosaurs or mosasaurs, but the long serpent-like -neck was probably very useful in helping the reptile catch fish and -other small animals for food. Plesiosaur remains range from middle -Triassic to late Cretaceous in age, and they have been found in -Cretaceous rocks in Texas. A short-necked plesiosaur which was collected -from Upper Cretaceous rocks near Waco is on display in the Strecker -Museum at Baylor University in Waco. - - Phytosaurs.— - -The phytosaurs were a group of crocodile-like reptiles which ranged from -6 to 25 feet in length (Pl. 42). They resembled the crocodiles both in -appearance and in their mode of life, but this similarity is only -superficial, and the phytosaurs and crocodiles are two distinct groups -of reptiles. - -The phytosaurs are exclusively Triassic in age and their remains have -been collected from Triassic rocks along the eastern margin of the High -Plains of Texas. - - Crocodiles and alligators.— - -These reptiles adapted themselves to the same type habitat that was -occupied by the phytosaurs, which preceded them. Crocodiles and -alligators were much larger and more abundant during Cretaceous and -Cenozoic time than they are today; the crocodiles first appeared in the -Cretaceous and the alligators in the Tertiary. The remains of both -crocodiles and alligators have been found in Texas, and one such -crocodile (_Phobosuchus_) represents the remains of the largest -crocodile yet discovered (Pl. 43). This specimen probably had an overall -length of 40 to 50 feet, and its massive skull was 6 feet long and -possessed exceptionally strong jaws. The remains of this great beast -were collected from exposures of Upper Cretaceous rocks along the Rio -Grande in Trans-Pecos Texas. - - Pterosaurs.— - -These were Mesozoic reptiles with bat-like wings supported by arms and -long thin “fingers” (Pl. 42). The pterosaurs were well adapted to life -in the air, and their light-weight bodies and wide skin-covered wings -enabled them to soar or glide for great distances. The earliest known -pterosaurs were found in lower Triassic rocks, and the group became -extinct by the end of the Cretaceous. During this time certain of these -creatures attained a wingspread of as much as 27 feet, but their bodies -were small and light. - - Dinosaurs.— - -The collective term “dinosaurs” (meaning terrible lizards) has been -given to that distinctive group of reptiles prominent in Mesozoic life -for some 140 million years. In size, the dinosaurs ranged from as little -as 1 foot to as much as 85 feet in length and from a few pounds to -perhaps 45 tons in weight. Some were _carnivorous_ (meat-eaters) but the -majority were _herbivorous_ (plant-eaters). Some were _bipedal_ (walked -on their hind-legs) while others were _quadrupedal_ (walked on all -fours), and although most of the dinosaurs were terrestrial in habitat, -aquatic and semi-aquatic forms were also present. - -According to the structure of their hip bones, the dinosaurs have been -divided into two great orders. These are the Saurischia (forms with -lizard-like pelvic girdle) and the Ornithischia (dinosaurs with a -bird-like pelvic girdle). - - [Illustration: Plate 43 - Dr. Brown, R. T. Bird, and Dr. Schaikjer with the skull of - _Phobosuchus_, an extinct crocodile from the Cretaceous of Trans-Pecos - Texas. - Photograph courtesy of the American Museum of Natural History.] - - Order Saurischia.— - -Dinosaurs belonging to this order were particularly abundant during the -Jurassic and are characterized by hip bones that are similar to those of -modern lizards. These dinosaurs were first discovered in rocks of -Triassic age and did not become extinct until the end of the Cretaceous. -The lizard-hipped reptiles are divided into two rather specialized -groups of dinosaurs: the _theropods_ (carnivorous bipedal dinosaurs that -varied greatly in size) and the _sauropods_ (herbivorous, quadrupedal, -semi-aquatic, usually gigantic dinosaurs). - - SUBORDER THEROPODA.— - -This type of saurischian dinosaur walked on bird-like hind limbs, and -they were exclusively meat-eating forms, such as _Allosaurus_ (Pl. 44) -of Jurassic age. Some theropods were exceptionally large and were -undoubtedly vicious beasts of prey. This assumption is borne out by such -anatomical features as the small front limbs with long sharp claws for -holding and tearing flesh, and the large strong jaws which were armed -with numerous, sharp, dagger-like teeth. The largest of all known -theropods was _Tyrannosaurus rex_ which, when standing on his hind -limbs, was almost 20 feet tall. Some individuals were as much as 50 feet -long, and _Tyrannosaurus_ is believed to have been among the most -vicious animals to ever inhabit our earth. A cast of the skull of one of -these great beasts is on display in the Texas Memorial Museum at Austin, -and a _Tyrannosaurus_ tooth has been found in the Big Bend National Park -in Trans-Pecos Texas. - - SUBORDER SAUROPODA.— - -The sauropods were the largest of all dinosaurs, and some attained a -length of 85 feet and probably weighed 40 to 50 tons (_Brontosaurus_, -Pl. 44). They were primarily herbivorous dinosaurs which had become -adapted to an aquatic or semi-aquatic type of existence and probably -inhabited lakes, rivers, and swamps. The tracks of sauropod dinosaurs -have been collected from Lower Cretaceous rocks in central Texas (Pl. 4) -and Upper Cretaceous beds in Big Bend National Park in Trans-Pecos -Texas. - - Order Ornithischia.— - -The ornithischian, or bird-hipped dinosaurs, were herbivorous reptiles -which were quite varied in form and size and appear to have been more -highly developed than the saurischians. This order includes the -duck-billed dinosaurs (ornithopods), the plate-bearing dinosaurs -(stegosaurs), the armored dinosaurs (ankylosaurs), and the horned -dinosaurs (ceratopsians). Ornithischian tracks are known from Cretaceous -rocks in central and Trans-Pecos Texas. - - SUBORDER ORNITHOPODA.— - -These unusual dinosaurs were predominantly bipedal, semi-aquatic, and -some (like the duck-billed dinosaurs) were highly specialized -(_Trachodon_, Pl. 45). - - SUBORDER STEGOSAURIA.— - -The stegosaurs were herbivorous, quadrupedal ornithischians with large -projecting plates down the back and heavy spikes on their tails. The -Jurassic dinosaur _Stegosaurus_ (Pl. 45) is most typical of the -plate-bearing forms. This creature weighed about 10 tons, was some 30 -feet long, and stood about 10 feet tall at the hips. _Stegosaurus_ is -characterized by a double row of large, heavy, pointed plates which run -along the animal’s back. These plates begin at the back of the skull and -stop near the end of the tail. The tail was also equipped with four or -more long curved spikes which were probably used as a means of defense. -The animal had a very small skull which housed a brain that was about -the size of a walnut, and it is assumed that these, and all other -dinosaurs, were of very limited intelligence. - -_Stegosaurus_ remains have not been discovered in Texas, but these, like -certain other of the extinct vertebrates, are mentioned because of their -interesting and unusual form. - - SUBORDER ANKYLOSAURIA.— - -The ankylosaurs were four-footed, herbivorous, Cretaceous dinosaurs -which had relatively flat bodies. The skull and back of the animal were -protected by bony armor, and the club-like tail was armed with spikes. -_Paleoscincus_ (Pl. 45), a typical ankylosaur, had large spines -projecting from along the sides of the body and tail. The armored spiked -back and the heavy club-like tail probably provided _Paleoscincus_ with -much-needed protection from the vicious meat-eating dinosaurs of -Cretaceous time. - - [Illustration: Plate 44 - SAURISCHIAN DINOSAURS] - - ALLOSAURUS × ¹/₁₈₀ - BRONTOSAURUS × ¹/₂₅₀ - - [Illustration: Plate 45 - ORNITHISCHIAN DINOSAURS] - - STEGOSAURUS × ¹/₉₀ - TRACHODON × ¹/₁₀₀ - PALEOSCINCUS × ¹/₂₅ - TRICERATOPS × ¹/₁₂₀ - - SUBORDER CERATOPSIA.— - -The ceratopsians, or horned dinosaurs, are another group of dinosaurs -that are known only from rocks of Cretaceous age. These plant-eating -dinosaurs possessed beak-like jaws, a bony neck frill which extended -back from the skull, and one or more horns. _Triceratops_ (Pl. 45) is -the largest of the horned dinosaurs (some forms were as much as 30 feet -long), and the skull measured 8 feet from the tip of the parrot-like -beak to the back of the neck shield. - - CLASS AVES.— - -Because of the fragile nature of their bodies, birds are seldom found as -fossils. In spite of this, however, some interesting and important -fossil bird remains have been discovered. - -The oldest known bird was found in Upper Jurassic rocks exposed in -Germany. This primitive bird, named _Archaeopteryx_, is little more than -a reptile with feathers. _Archaeopteryx_ was a pigeon-sized creature -which had scales as well as feathers, a lizard-like tail, a toothed -beak, and other definitely reptilian characteristics. - -During late Cretaceous time the birds underwent changes that resulted in -forms similar to those that are living today, and most of the -present-day birds had developed by the end of the Tertiary. - -Although not commonly found, fossil birds have been recorded from -certain of the Cenozoic rocks of Texas. - - CLASS MAMMALIA.— - -The mammals are animals that are born alive and fed with milk from the -mother’s breast. They are warm-blooded, air-breathing, have a protective -covering of hair, and are the most advanced of all vertebrates. The -foregoing features are the more typical mammalian characteristics, but -exceptions to these are found in certain mammals. - -Mammals first appeared in the Jurassic and were probably derived from -some form of mammal-like reptile. Although rare during the Mesozoic, -mammals underwent rapid development and expansion during the Cenozoic, -and during this era certain types of mammals became extremely large and -assumed many bizarre shapes. The majority of these unusual forms lived -but a short time but are well known from their fossils, and the remains -of some of these animals which inhabited Texas during the Cenozoic may -be seen in the Texas Memorial Museum at Austin. - -Recent mammalian classification recognizes several subclasses and -numerous orders and suborders, but the treatment of the mammals in a -publication of this nature must of necessity be somewhat brief and no -attempt at detailed classification is made. - - Subclass Allotheria.— - -The allotherians first appeared during the Jurassic and underwent -considerable development in the late Cretaceous and early Tertiary. -Included in this subclass are the _multituberculates_ which are a group -of small rodent-like animals that were probably the earliest of the -herbivorous mammals. These animals were probably never very numerous, -and they became extinct during the early part of Eocene time. - - Subclass Theria.— - -Members of this subclass are first known from rocks of Jurassic age, and -they constitute the largest group of mammals that are living today. -Therians undergo considerable development before they are born and at -birth typically resemble the fully developed animal. This subclass has -been divided into several orders but only the more important ones are -discussed here. - - Order Edentata.— - -The edentates are a rather primitive group of mammals which are -represented by such living forms as the anteaters, tree sloths, and -armadillos. Members of this group were common in the southern part of -the United States in Pleistocene and Pliocene time, and fossil edentates -have been reported from rocks of this age in Texas. One such form was -_Mylodon_ (Pl. 46), one of the extinct giant ground sloths. These huge -sloths were quite heavy and some of them stood as much as 15 feet tall; -these great creatures were the forerunners of the modern tree sloths of -South America. The mounted skeleton of one of these giant ground sloths -is displayed in the Texas Memorial Museum. - - [Illustration: Plate 46 - CENOZOIC MAMMALS] - - ENTELODONT × ¹/₃₅ - GLYPTODON × ¹/₅₀ - MYLODON × ¹/₉₀ - -Another interesting representative of this order was the glyptodont. -These peculiar mammals, which were ancestral to the present-day -armadillos, developed at about the same time as the ground sloths. -_Glyptodon_ (Pl. 46), a typical glyptodont that has been reported from -the Pleistocene of Texas, is quite characteristic of this group. This -armadillo-like beast had a solid turtle-like shell that in some forms -was as much as 4 feet high. From the front of the bone capped head to -the tip of its tail, a large individual might be as much as 15 feet -long. The thick heavy tail was protected by a series of bony rings, and -in some species the end of the tail was developed into a bony heavily -spiked club. The _carapace_ (hard outer shell) of a large glyptodont is -mounted at the Texas Memorial Museum. - - Order Carnivora.— - -Animals belonging to this order are called carnivores and are -characterized by clawed feet and by teeth which are adapted for tearing -and cutting flesh. The carnivores, or meat-eaters, were first -represented by an ancient group of animals called _creodonts_, and this -short-lived group first appeared in the Paleocene and were extinct by -the end of the Eocene. They ranged from the size of a weazel to that of -a large bear, and their claws were sharp and well developed. Their -teeth, however, were not as specialized as those of modern carnivores, -and the creodont brain was relatively small. It is assumed that these -animals had a very low order of intelligence when compared to the more -advanced carnivores of today. - -These early meat-eaters were followed by more specialized carnivores -which developed throughout Cenozoic time. Some examples of these are the -saber-tooth cat _Dinobastis_ (Pl. 47) and the dire wolf _Canis diris_ -(Pl. 47), both of which have been reported from the Texas Pleistocene. -Some remains of these unusual forms, representing the cat and dog -families, are on display at the Texas Memorial Museum. - - Order Pantodonta.— - -Pantodonts, known also as _amblypods_, were primitive, hoofed, -herbivorous animals. They were distinguished by a heavy skeleton, short -stout limbs, and blunt spreading feet. The pantodonts appeared first -during Paleocene time and had become extinct by the end of the -Oligocene. - - Order Dinocerata.— - -The members of this order are an extinct group of gigantic mammals -commonly called _uintatheres_. _Uintatherium_ (Pl. 48), which is typical -of the group, had three pairs of blunt horns, and the males had -dagger-like upper tusks. Some of the uintatheres were as large as a -small elephant and stood as much as 7 feet tall at the shoulders. The -size of the brain in relation to the size of the body suggests that -these animals were not as intelligent as most mammals. Uintatheres are -known from rocks ranging from Paleocene to Eocene in age. Uintathere -remains have been reported from Big Bend National Park in Trans-Pecos -Texas. - - Order Proboscidea.— - -The earliest proboscideans, the elephants and their relatives, first -appeared in the late Eocene of Africa and were about the size of a small -modern elephant but had larger heads and shorter trunks. Proboscidean -development is marked by an increase in size, change in skull and tooth -structure, and elongation of the trunk. Two well-known fossil -proboscideans are the _mammoth_ and the _mastodon_, both of which -inhabited Texas during Pleistocene time. The mastodons resembled the -elephants, but the structure of their teeth was quite different (fig. -25). Moreover, the mastodon skull was lower than that of the elephant -and the tusks were exceptionally large—some reaching a length of 9 feet. - - [Illustration: Plate 47 - CENOZOIC MAMMALS] - - DINOBASTIS × ¹/₂₀ - CANIS DIRUS × ¹/₁₅ - HYRACOTHERIUM × ¹/₁₀ - PLIOHIPPUS × ¹/₂₀ - -There were several types of mammoths, and the _woolly mammoth_ is -probably the best known. This animal lived until the end of the -Pleistocene and, like the woolly rhinoceros discussed below, is known -from ancient cave paintings and frozen remains. Information gathered -from these sources indicates that this great beast had a long coat of -black hair with a woolly undercoat (Pl. 49). - -[Illustration: Fig. 25. Sketches of Pleistocene (a) mastodon tooth (×⅙) - and (b) mammoth tooth (×⅙).] - -During the Pleistocene, mammoths were widespread over the United States, -and their remains are abundant in many stream deposits of this age. -Proboscidean bones have been reported from Pleistocene rocks in many -parts of Texas, where they are commonly found in sand and gravel pits. - - Order Perissodactyla.— - -The perissodactyls, or odd-toed animals, are mammals in which the -central toe on each limb is greatly enlarged. Modern representatives -include the horses, rhinoceroses, and tapirs. Extinct members of the -Perissodactyla include the _titanotheres_, _chalicotheres_, and -_baluchitheres_, all of which grew to tremendous size and took on many -unusual body forms. - - HORSES.— - -One of the first perissodactyls was _Hyracotherium_ (also called -_Eohippus_), which is the earliest known horse (Pl. 47). This small -animal, whose remains have been found in Big Bend National Park, was -about 1 foot high and his teeth indicate a diet of soft food. Following -the first horse, there is a long series of fossil horses which provide -much valuable information on the history of this important group of -animals. - -The record of the development of the horse is well represented in Texas, -and the bones and teeth of fossil horses are common in certain parts of -the State. Fossils of this type have been reported from the Tertiary of -the Trans-Pecos, Gulf Coastal Plain, and High Plains regions of Texas, -and the teeth of Pleistocene horses have been found in sand and gravel -pits in many parts of the State. Horse teeth (fig. 26) are particularly -useful fossils as they may be accurately identified and used to -determine the age of the rocks in which they are found. - - [Illustration: Fig. 26. Typical Pliocene horse tooth. Top view (a) and - lateral view (b) of molar tooth (×½).] - - TITANOTHERES.— - -This group of odd-toed mammals appeared first in the Eocene, at which -time they were about the size of a sheep. By Middle Oligocene time they -had increased to gigantic proportions but still had a small and -primitive brain. _Brontotherium_ (Pl. 48) was slightly rhinoceros-like -in appearance and is believed to be the largest land animal that ever -inhabited the North American continent. This animal was about 8 feet -tall at the shoulders; a large bony growth protruded from the skull and -this was extended into a flattened horn, which was divided at the top. - - [Illustration: Plate 48 - TERTIARY MAMMALS] - - UINTATHERIUM × ¹/₄₅ - BRONTOTHERIUM × ¹/₃₅ - -Although the titanotheres underwent rapid development during the early -Tertiary, these huge beasts became extinct during the middle of the -Oligocene epoch. Titanothere remains have been reported from the -Trans-Pecos region of Texas. - - CHALICOTHERES.— - -The chalicotheres were in some ways like the titanotheres, but they also -exhibited many peculiarities of their own. The head and neck of -_Moropus_, a typical chalicothere, were much like that of a horse, but -the front legs were longer than the hind legs, and the feet resembled -those of a rhinoceros except that they bore long claws instead of hoofs. -The chalicotheres lived in North America from Miocene until Pleistocene -time but were probably never very numerous, and their remains have not -yet been discovered in Texas. - - RHINOCEROSES.— - -The rhinoceroses are also odd-toed animals, and there are many -interesting and well-known fossils in this group. The _woolly -rhinoceros_ (Pl. 49) was a Pleistocene two-horned form that ranged from -southern France to northeastern Siberia. The woolly rhinoceros is well -known from complete carcasses recovered from the frozen tundra of -Siberia and from remains that were found preserved in an oil seep in -Poland. These unusual specimens plus cave paintings made by early man -have given a complete and accurate record of this creature. Although the -woolly rhinoceros has not been reported from Texas, other fossil -rhinoceroses have been found in the High Plains and Gulf Coastal Plain -of Texas. These fossils have been found in rocks ranging from Middle -Oligocene to late Pliocene in age. - -_Baluchitherium_, the largest land mammal known to science, was a -hornless rhinoceros that lived in late Oligocene and early Miocene time. -This immense creature measured approximately 25 feet from head to tail, -stood almost 18 feet high at the shoulder, and must have weighed many -tons. Remains of these creatures have not been discovered in North -America, and they appear to have been restricted to Central Asia. - - Order Artiodactyla.— - -The artiodactyls are the even-toed hoofed mammals and include such -familiar forms as pigs, camels, deer, goats, sheep, and hippopotamuses. -This is a large and varied group of animals, but the basic anatomical -structure of the limbs and teeth show well the relationship between the -different forms. Artiodactyls are abundant fossils in rocks ranging from -Eocene to Pleistocene in age and are common in rocks of this age in -Texas. - - ENTELODONTS.— - -These giant pig-like artiodactyls lived during Oligocene and early -Miocene time and were distinguished by a long heavy skull that held a -relatively small brain. The face was marked by large knobs which were -located beneath the eyes and on the underside of the lower jaw, and -although these knob-like structures were blunt they had the appearance -of short horns. Certain of these giant swine attained a height of 6 feet -at the shoulders and had skulls that measured 3 feet in length (Pl. 46). -Entelodont remains have been found in the Miocene of the Texas Coastal -Plain. - - CAMELS.— - -The first known camels have been reported from rocks of upper Eocene -age, and these small forms underwent considerable specialization of -teeth and limbs as they developed in size. Many of the camels that lived -during the middle Cenozoic had long legs which were well adapted to -running and long necks which would have allowed the animals to browse on -the leaves of tall trees. - -The earliest known Texas camels were found in rocks of Oligocene age, -and camels, like horses, must have been abundant in Texas during the -Pleistocene for their fossilized remains are common in many parts of the -State. - - [Illustration: Plate 49 - CENOZOIC MAMMALS] - - WOOLLY RHINOCEROS × ¹/₂₀ - WOOLLY MAMMOTH × ¹/₄₀ - - - - - BOOKS ABOUT FOSSILS - - -The following books are recommended for the reader who wants to know -more about fossils and fossil collecting. The publications listed below -cover various phases of historical geology and paleontology and range -from children’s books to the more technical publications of the -professional paleontologist. This list, however, is by no means -all-inclusive and many other interesting and useful publications are -available. - - - GENERAL WORKS - - -Dunbar, C. O. (1959) Historical geology, John Wiley and Sons, New York. - - College-level text, well written and well illustrated. - - -Moore, R. C. (1958) Introduction to historical geology, McGraw-Hill Book -Co., New York. - - College-level presentation of earth history. Many illustrations of - fossils. - - -Moore, Ruth (1953) Man, time, and fossils, Alfred Knopf, New York. - - A readable account of fossils and their development throughout - geologic time. - - -Panghorn, M. W., Jr. (1957) Earth for the layman, American Geological -Institute, Washington, D. C. - - Contains many valuable references. - - -Raymond, P. E. (1950) Prehistoric life, Harvard University Press, -Cambridge, Mass. - - College-level text. - - -Richards, H. G. (1953) Record of the rocks, Ronald Press, New York. - - College-level earth history text. - - -Simpson, G. G. (1953) Life of the past, Yale University Press, New -Haven, Conn. - - Thorough, yet readable, introduction to paleontology. - - -Stirton, R. A. (1959) Time, life, and man: the fossil record, John Wiley -and Sons, New York. - - An introductory college text, most of which is of interest to adult - level general readers. - - -Note: _See also_ sections on Paleontology and Fossils _in_ Encyclopedia -Americana, Encyclopaedia Britannica, and others. - - - NONTECHNICAL AND JUVENILE - - -Andrews, R. C. (1953) All about dinosaurs, Random House, New York. - - Interesting and readable dinosaur book for junior high and high-school - age. - - -Andrews, R. C. (1956) All about strange beasts of the past, Random -House, New York. - - Interesting and easy to read, this book deals largely with extinct and - unusual mammals (junior high and high school). - - -Colbert, E. H. (1945) The dinosaur book, American Museum of Natural -History, New York. - - A classic among “popular” dinosaur books. For all age levels. - - -Colbert, E. H. (1957) Dinosaurs, American Museum of Natural History, New -York. - - This little booklet provides a well-illustrated introduction to the - dinosaurs. For high school and adult-level readers. - - -Dickinson, Alice (1954) First book of prehistoric animals, Franklin -Watts, Inc., New York. - - Easy to read, well-illustrated book for grade-school age. - - -Dunkle, D. H. (1957) The world of the dinosaurs, Smithsonian -Institution, Washington, D. C. - - An easy to understand, amply illustrated introduction to the dinosaurs - (high school-adult level). - - -Fenton, C. L. (1937) Life long ago, The John Day Co., New York. - - Very good for advanced grade and high-school age. - - -Heal, Edith (1930) How the world began, Thomas S. Rockwell Co., Chicago. - - An account of the beginnings of life. For upper grade through - high-school age. - - -Markman, H. C. (1954) Fossils, Denver Museum of Natural History, Denver, -Colo. - - A well-illustrated general survey of fossils. For adult-level readers. - - -Matthews III, W. H. (1962) Fossils: An introduction to prehistoric life, -Barnes and Noble, Inc., New York, [“In preparation” at time of first -printing of Guidebook No. 2.] - - This publication contains many collecting aids and much background - material for amateur collectors. Contains also a brief review of earth - history. - - -Matthews III, W. H. (1963) Wonders of the dinosaur world, Dodd, Mead & -Co., New York. - - Well illustrated, non-technical presentation of dinosaurs. For - junior-high and high-school teachers. - - -Parker, B. M. (1942) Stories read from the rocks, Basic Science -Education Series, Row, Peterson and Co., Evanston, Ill. - - Well written and colorfully illustrated. For advanced grades and - junior high. - - -Parker, B. M. (1948) Animals of yesterday, Basic Science Education -Series, Row, Peterson, and Co., Evanston, Ill. - - Well written and colorfully illustrated. For advanced grades and - junior high. - - -Shaver, R. H. (1959) Adventures with fossils, Geological Survey, Indiana -Department of Conservation, Bloomington, Ind. - - Collection hints and general information on fossils. Particularly for - the lower grades. - - -Shuttlesworth, D. E. (1957) Real book of prehistoric life, Garden City -Books, Garden City, N. Y. - - Survey of prehistoric life. For grade and junior-high levels. - - - COLLECTING HELPS - - -Brown, Vinson (1954) How to make a home nature museum, Little, Brown and -Co., Boston. - - Contains suggestions for collecting, mounting, and displaying fossils - and other objects of nature. - - -Camp, C. L., and Hanna, G. D. (1937) Methods in paleontology, University -of California Press, Berkeley. - - Excellent discussion of collecting and preparation techniques. - - -Casanova, Richard (1957) An illustrated guide to fossil collecting, -Natureograph Co., San Martin, Calif. - - Has collecting hints and fossil localities for most of the States. - - -Collinson, C. C. (1959) Guide for beginning fossil hunters, Educational -Series 4, Illinois State Geological Survey, Urbana. - - Clearly written, well illustrated, particularly for the lower grades. - - -Goldring, Winifred (1950) Handbook of paleontology for beginners and -amateurs, New York State Museum, Albany, N. Y. - - A complete summary of paleontology. For the advanced collector. - - -La Rocque, A., and Marple, M. F. (1955) Ohio fossils, Ohio Division of -Geological Survey, Bulletin 54, Columbus, Ohio. - - Rather comprehensive treatment of the invertebrates with several - useful keys for fossil identification. - - -Livingston, V. E., Jr. (1959) Fossils in Washington, Division of Mines -and Geology, Department of Conservation, Olympia, Wash. - - An introduction to the geology and fossils of Washington. Contains - guide to collecting localities. - - -Simpson, B. W. (1958) Gem trails of Texas, Bessie W. Simpson, Granbury, -Texas. - - Field guide to Texas mineral, rock, and fossil locations. Contains - numerous maps and well-described collecting localities. - - -Unklesbay, A. G. (1955) Common fossils of Missouri, University of -Missouri Bulletin, Handbook 4, Columbia, Mo. - - Written for the amateur; contains much general information of interest - to the beginning collector. - - - REFERENCE WORKS - - -Arnold, C. A. (1947) An introduction to paleobotany, McGraw-Hill Book -Co., New York. - - College-level textbook. - - -Beerbower, J. R. (1960) Search for the past, Prentice-Hall, Inc., -Englewood Cliffs, N. J. - - Good background text. Well illustrated. Has section on vertebrates. - - -Colbert, E. H. (1955) Evolution of the vertebrates, John Wiley and Sons, -New York. - - Comprehensive and technical treatment of vertebrate fossils. - - -Cushman, J. A. (1948) Foraminifera, their classification and economic -use, Harvard University Press, Cambridge, Mass. - - College-level text containing large numbers of descriptions and - illustrations of foraminifera. - - -Easton, W. H. (1960) Invertebrate paleontology, Harper & Bros., Inc., -New York. - - College-level text. Good illustrations, useful for identification. - - -Fenton, C. L., and Fenton, M. A. (1958) The fossil book, Doubleday and -Co., New York. - - Comprehensive, easy-to-read, beautifully illustrated treatment of all - types of fossils. - - -Jones, D. J. (1956) Introduction to microfossils, Harper and Brothers, -New York. - - College-level textbook with considerable information on collection, - preparation, and the types of microfossils. - - -Moore, R. C., et al. (1953-1959) Treatise on invertebrate paleontology, -Geological Society of America and University of Kansas, Lawrence, -Kansas. - - A technical reference for the more advanced collector. It is issued in - several parts and contains latest classification. - - -Moore, R. C., Lalicker, C. G., and Fisher, A. G. (1953) Invertebrate -fossils, McGraw-Hill Book Co., New York. - - College-level reference with fine illustrations. Of value for purposes - of identification. - - -Romer, A. S. (1945) Vertebrate paleontology, University of Chicago -Press, Chicago. - - A college-level textbook with numerous illustrations. - - -Shimer, H. W. (1933) Introduction to the study of fossils, The Macmillan -Company, New York. - - A relatively simple college-level presentation of plant and animal - fossils. - - -Shimer, H. W., and Shrock, R. R. (1944) Index fossils of North America, -John Wiley and Sons, New York. - - Comprehensive survey of the more common fossils of North America. - Useful to the advanced collector and a most useful aid for fossil - identification. - - -Shrock, R. R., and Twenhofel, W. H. (1953) Principles of invertebrate -paleontology, McGraw-Hill Book Co., New York. - - Useful college-level reference for advanced collectors. - - - SELECTED REFERENCES ON TEXAS FOSSILS[2] - - -*Adkins, W. S. (1920) The Weno and Pawpaw formations of the Texas -Comanchean: Univ. Texas Bull. 1856. - - Descriptions and illustrations of many common Cretaceous fossils. - - -*Adkins, W. S. (1928) Handbook of Texas Cretaceous fossils: Univ. Texas -Bull. 2838. - - Lists all fossils described from the Texas Cretaceous prior to 1928, - with many useful illustrations. - - -*Adkins, W. S., and Winton, W. M. (1919) Paleontological correlation of -the Fredericksburg and Washita formations of north-central Texas: Univ. -Texas Bull. 1945. - - Contains descriptions and illustrations of many common Lower - Cretaceous fossils of north-central Texas. - - -Clarke, W. B., and Twitchell, M. W. (1915) The Mesozoic and Cenozoic -Echinodermata of the United States: U. S. Geological Survey Monograph -54, Washington, D. C. - - A valuable guide to the Mesozoic and Cenozoic echinoderms of Texas. - - -*Frizzell, D. L. (1954) Handbook of Cretaceous Foraminifera of Texas: -Univ. Texas, Bureau Econ. Geol. Rept. Inves. No. 22. - - A technical, but invaluable aid in the study of Texas Cretaceous - microfossils. - - -*Girard, R. M. (1959) Bibliography and index of Texas geology, -1933-1950: Univ. Texas Pub. 5910. - - This valuable reference guide contains many references to Texas - fossils. Note especially entries under Paleontology in the index. - - -Heuer, Edward (1958) Comments on the nomenclature revision of the Strawn -and Canyon megafossil plates, _in_ A guide to the Strawn and Canyon -Series of the Pennsylvanian System in Palo Pinto County, Texas, An -Occasional Publication of the North Texas Geological Society, Wichita -Falls, Texas. - - Contains illustrations and latest name changes of many of the more - common Pennsylvanian fossils of north Texas. - - -*King, R. E. (1930) Geology of the Glass Mountains, Part II, Faunal -summary and correlation of the Permian formations with description of -Brachiopoda: Univ. Texas Bull. 3042. - - Contains descriptions and illustrations of numerous brachiopods from - the Glass Mountains of Trans-Pecos Texas. - - -*Lee, Wallace, et al. (1939) Stratigraphic and paleontologic studies of -the Pennsylvanian and Permian rocks of north-central Texas: Univ. Texas -Pub. 3801. - - Contains an extensive faunal list and important collecting localities - for Pennsylvanian invertebrates. - - -*Moore, R. C., and Jeffords, R. M. (1944) Description of lower -Pennsylvanian corals from Texas and adjacent states: Univ. Texas Pub. -4401, pp. 77-208. - - Describes and illustrates many of the more common Pennsylvanian - corals. - - -*Plummer, F. B. (1943) The Carboniferous rocks of the Llano region of -central Texas: Univ. Texas Pub. 4329. - - Contains geologic map, locality data, and illustrations of many - Carboniferous fossils. - - -*Plummer, F. B., and Moore, R. C. (1921) Stratigraphy of the -Pennsylvanian formations of north-central Texas: Univ. Texas Bull. 2132. - - Describes and illustrates many of the more common Pennsylvanian - fossils of north-central Texas. - - -*Plummer, F. B., and Scott, Gayle (1937) Upper Paleozoic ammonites in -Texas: Univ. Texas Bull. 3701, pt. 1. - - *Renick, B. C., and Stenzel, H. B. (1931) The lower Claiborne of the - Brazos River, Texas: Univ. Texas Bull. 3101, pp. 73-108. - - -Contains discussion and illustrations of many common Tertiary fossils. - - Sellards, E. H. (1955) Texas through 250 million years: Museum Notes - No. 4, Texas Memorial Museum, Austin. - - -This little booklet provides a short geologic history of Texas along -with a review of oil in Texas. - - *Sellards, E. H., Adkins, W. S., and Plummer, F. B. (1933) The geology - of Texas, Vol. I, Stratigraphy: Univ. Texas Bull. 3232 (August 22, - 1932). - - -This important publication will give the advanced collector much -valuable information on the distribution of the rocks of Texas. Complete -with geologic map. - - Stanton, T. W. (1947) Studies of some Comanche pelecypods and - gastropods: U. S. Geological Survey Prof. Paper 211, Washington, D. C. - - -Describes and illustrates most of the more common Lower Cretaceous -pelecypods and gastropods of the State. - - *Stenzel, H. B., Krause, E. K., and Twining, J. T. (1957) Pelecypoda - from the type locality of the Stone City beds (Eocene) of Texas: Univ. - Texas Pub. 5704. - - -Descriptions and illustrations of many of the more common Tertiary clams -and oysters. - - *Stephenson, L. W. (1941) The larger invertebrate fossils of the - Navarro group of Texas: Univ. Texas Pub. 4101. - - -Contains descriptions of many common Upper Cretaceous invertebrates -(exclusive of corals and crustaceans). - - Stephenson, L. W. (1952) Larger invertebrate fossils of the Woodbine - formation (Cenomanian) of Texas: U. S. Geological Survey Prof. Paper - 242, Washington, D. C. - - -*Winton, W. M. (1925) The geology of Denton County: Univ. Texas Bull. -2544. - - Illustrates and discusses the occurrence of many Cretaceous fossils. - - -*Winton, W. M., and Adkins, W. S. (1920) The geology of Tarrant County: -Univ. Texas Bull. 1931. - - Contains many illustrations of common north Texas Cretaceous fossils. - - - - - GLOSSARY - - -Amber—a hard, yellowish, translucent, fossilized plant resin. - -Ammonite—ammonoid cephalopod with complexly wrinkled suture pattern; - member of subclass Ammonoidea. - -Anterior—front or fore. - -Anus—the terminal opening of the alimentary canal, through which waste - matter is discarded from the body. - -Aperture—the opening of shells, cells, etc. - -Aragonite—calcium carbonate (CaCO₃) crystallizing in a different form - than calcite. In shells it is chalky and opaque; is less stable than - calcite. - -Archeozoic—the oldest known geological era; early Precambrian time. - -Articulated—joined by interlocking processes or by teeth and sockets. - -Asymmetrical—without or lacking symmetry. - -Bilateral—pertaining to the two halves of a body as symmetrical and - mirror images of each other. - -Binomial nomenclature—system of scientific nomenclature requiring two - names: generic and trivial. - -Blastoid—stalked echinoderm with bud-like calyx usually consisting of 13 - plates; member of class Blastoidea. - -Brachiopod—bivalved marine invertebrate; member of phylum Brachiopoda. - -Brackish—a mixture of salt and fresh waters. - -Burrow—a hole in the ground, rock, wood, etc., made by certain animals - for shelter or while gathering food. - -Calcareous—composed of, or containing, calcium carbonate; limy. - -Calcite—calcium carbonate (CaCO₃) crystallizing in a different form than - aragonite. In shells it is translucent and more stable than aragonite. - -Cambrian—the first (oldest) period of the Paleozoic era. - -Calyx—in corals the bowl-shaped depression in the upper part of the - skeleton; in stalked echinoderms that part of the body which contains - most of the soft parts. - -Caprinid—a Cretaceous pelecypod that is typically coiled in the form of - a ram’s horn. - -Carapace—the hard protective covering that forms the exoskeleton of many - invertebrates; in arthropods it is usually chitinous or - calcaro-chitinous. - -Carbonization—the process of fossilization whereby organic remains are - reduced to carbon or coal. - -Cast—the impression taken from a mold. - -Cenozoic—the latest era of geologic time, following the Mesozoic era and - extending to the present. - -Cephalon—the head; in trilobites the anterior body segment forming the - head. - -Cephalopod—marine invertebrate with well-defined head and eyes and with - tentacles around the mouth; member of class Cephalopoda, phylum - Mollusca; includes squids, octopuses, pearly nautilus. - -Ceratite—an ammonoid cephalopod with suture composed of rounded saddles - and jagged lobes; member of subclass Ammonoidea. - -Chert—a cryptocrystalline variety of silica; flint is a variety of - chert. - -Chitin—a horn-like substance, found in the hard parts of many animals, - such as beetles, crabs, etc. - -Chitinous—composed of chitin. - -Cirri—in crinoids, the jointed appendages which branch off the side of - the stem or from the base of some crinoid stems. - -Coelenterate—invertebrates characterized by a hollow body cavity, radial - symmetry, and stinging cells; a member of phylum Coelenterata; - includes jellyfishes, corals, sea anemones. - -Colonial—in biology refers to the way in which some invertebrates live - in close association with, and are more or less interdependent upon, - each other; colonial corals, hydroids, etc. - -Columella—a small column or central axis; in corals the small rod or - axial pillar in the center of the corallite; in gastropods the solid - or perforate pillar formed by the union of the successive coils of a - conispiral shell. - -Columnal—one of the disk-shaped segments of a crinoid stalk. - -Concentric—having a common center, as circles; refers to shell markings - that are parallel to shell margin. - -Concretion—nodular or irregular masses in sedimentary rocks and usually - formed around a central core, which is often a fossil. - -Conical—cone-shaped. - -Conodont—minute tooth-like fossils found in certain Paleozoic rocks; - their origin is not definitely known, but they may have been part of - some type of extinct fish. - -Coral—bottom-dwelling marine invertebrate that secretes calcareous hard - parts; member of class Anthozoa, phylum Coelenterata. - -Corallite—the skeleton formed by an individual coral animal; may be - solitary or form part of a colony. - -Corallum—the skeleton of a coral colony. - -Corona—crown; in echinoids the main part of the skeleton consisting of - symmetrically arranged calcareous plates. - -Coprolite—the fossil excrement of animals. - -Correlation—the process of demonstrating that certain strata are closely - related to each other or that they are stratigraphic equivalents. - -Cretaceous—the third and last period of the Mesozoic era. - -Cystoid—an extinct stemmed echinoderm with calyx composed of numerous - irregularly arranged plates; member of class Cystoidea. - -Dendritic—resembling a tree, branching. - -Dentition—the system or arrangement of teeth peculiar to any given - animal. - -Devonian—the fourth oldest period of the Paleozoic era, follows the - Silurian, precedes the Mississippian. - -Dip—the angle of inclination which the bedding plane of rocks makes with - a real or imaginary horizontal line. - -Distillation—in fossils that process by which volatile organic matter is - removed, leaving a carbon residue. - -Dolomite—a mineral composed of calcium magnesium carbonate (CaMg(CO₃)₂). - -Dorsal—pertaining to the back. - -Echinoderm—a marine invertebrate with calcareous exoskeleton and usually - exhibiting a five-fold radial symmetry; member of phylum - Echinodermata; includes cystoids, blastoids, crinoids, starfishes, and - sea urchins. - -Echinoid—bottom-dwelling, unattached marine invertebrate with - exoskeleton of calcareous plates covered by movable spines; member of - class Echinoidea; sea urchins, heart urchins, biscuit urchins. - -Endoskeleton—the internal supporting structure of an animal. - -Eocene—the next to earliest of the Tertiary epochs, follows the - Paleocene and precedes the Oligocene. - -Equivalved—right and left valves subequal and (except for hinge - structures) comprising mirror images of each other. - -Evolution—a term applied to those methods or processes and to the sum of - those processes whereby organisms change through successive - generations. - -Exoskeleton—an external skeleton, or hard covering for the protection of - soft parts, particularly among invertebrates. - -Fault—the displacement of rocks along a zone of fracture. - -Fauna—an assemblage of animals (living or fossil) living in a given - place at a given time. - -Flank—the side or lateral portion of anything. - -Flora—an assemblage of plants (living or fossil) living in a given place - at a given time. - -Fold—in brachiopods, a major rounded elevation of shell which affects - both inner and outer shell surfaces. - -Foramen—in brachiopods, the opening in the pedicle valve near the beak - where the pedicle extends through the shell. - -Foraminifer—a protozoan usually possessing a calcareous, perforated, - chambered shell, but shell may be chitinous or agglutinated; a member - of the order Foraminifera, phylum Protozoa. - -Formation—a rock unit useful for mapping and distinguished primarily on - the basis of lithologic characters. - -Fossil—the remains or traces of organisms buried by natural causes and - preserved in the earth’s crust. - -_Guide fossil_—a fossil which, because of its limited vertical but wide - horizontal distribution, is of value as a guide or index to the age of - the rocks in which it is found. - -Fossiliferous—containing fossilized organic remains. - -Fusulinid—a spindle-shaped foraminifer: test shaped like a grain of - wheat. - -Gastrolith—highly polished well-rounded pebbles found associated with - certain reptilian fossils; “stomach stones.” - -Gastropod—a terrestrial or aquatic invertebrate, typically possessing a - single-valved, calcareous, coiled shell; member of class Gastropoda, - phylum Mollusca: snails and slugs. - -Geologic age—the age of an object as stated in terms of geologic time - (e.g., a Pennsylvanian fern, Cretaceous dinosaur). - -Geologic map—map showing distribution of rock outcrops, structural - features, mineral deposits, etc. - -Geologic range—the known duration of an organism’s existence throughout - geologic time (e.g., Cambrian to Recent for brachiopods). - -Glauconite—a greenish mineral commonly formed in marine environments and - essentially a hydrous silicate of iron and potassium. - -Goniatite—an ammonoid cephalopod with suture composed of smooth saddles - and simple angular lobes; member of subclass Ammonoidea. - -Graptolite—an extinct, marine, colonial organism with chitinous hard - parts; believed to belong to subphylum Hemichordata of phylum - Chordata. - -Guide fossil—see Fossil. - -Habitat—the physical environment in which an organism lives. - -Hinge-line—in brachiopods, the edge of the shell where the two valves - articulate; in pelecypods, the dorsal margin of the valve which is in - continual contact with the opposite valve. - -Igneous rock—rocks which have solidified from lava or molten rock called - magma. - -Index fossil—see Fossil. - -Inequivalved—opposite valves unlike in shape or size, or both. - -Jurassic—second oldest period of the Mesozoic; follows the Triassic, - precedes the Cretaceous. - -Keel—a strong continuous ridge along the ventral side of ammonites. - -Larva—the young form of some animals before they assume the mature - shape. - -Lateral—side or to the side. - -Lithology—the study and description of rocks based on the megascopic - (with the naked eye) examination of samples. Used also to refer to the - texture and composition of any given rock sample. - -Living chamber—in mollusks, that part of the shell which is occupied by - the living animal. - -Lobe—in cephalopods, the backward flexure of the suture or septum. - -Longitudinal—in a direction parallel with the length. - -Lophophore—in brachiopods, a tentacle-bearing appendage attached to the - anterior surface of the mantle cavity. - -Mantle—in mollusks and brachiopods, a layer of tissue containing cells - that secrete the shell. - -Meso-—a prefix signifying middle. - -Mesozoic—that era of geologic time that precedes the Cenozoic and - follows the Paleozoic. - -Miocene—fourth oldest epoch of the Tertiary period; follows the - Oligocene, precedes the Pliocene. - -Mississippian—fifth oldest period of the Paleozoic: follows the - Devonian, precedes the Pennsylvanian. - -Multicellular—composed of more than one cell. - -Nacreous—pearly. - -Node—a knob. - --oid—a suffix meaning “in the form of.” - -Oligocene—the third oldest epoch of the Tertiary period: precedes the - Miocene, follows the Eocene. - -Operculum—the lid or covering of the aperture of certain shells. - -Oral—referring to the mouth or aperture. - -Orbitoidids—foraminifers with large typically disk-shaped tests. - -Ordovician—second oldest period of the Paleozoic era; follows the - Cambrian, precedes the Silurian. - -Ossicle—loosely used as a small plate. - -Paleocene—oldest epoch of the Tertiary period; precedes the Eocene. - -Paleozoic—that era of geologic time that follows Precambrian time and - precedes the Mesozoic era. - -Pedicle opening (pedicle foramen)—see Foramen. - -Pelecypod—a bivalved aquatic invertebrate; member of class Pelecypoda, - phylum Mollusca. - -Pennsylvanian—the sixth oldest period of the Paleozoic era; follows the - Mississippian, precedes the Permian. - -Period—a division of geologic time (Pl. 1). - -Periostracum—the horny outer covering or epidermis on shells. - -Permian—seventh and last period of the Paleozoic. - -Permineralization—that process by which mineral matter has been added to - the original shell material by precipitation in the interstices rather - than replacing the original shell material. - -Phosphatic—containing or pertaining to phosphate minerals. - -Phylum—one of the primary divisions of the animal or vegetable kingdoms. - -Planispiral—shell coiled in one plane. - -Pleistocene—earliest epoch of Quaternary period, Cenozoic era; follows - Pliocene epoch of Tertiary period, precedes Recent epoch of - Quaternary. - -Pleural—referring to the side or ribs; in trilobites, refers to lateral - portions of thorax and pygidium. - -Pliocene—latest epoch of Tertiary period of Cenozoic era; follows - Miocene epoch and precedes Pleistocene epoch of Quaternary period. - -Polygonal—many sided or having many-sided plates. - -Polyp—a many-tentacled aquatic coelenterate animal, typically - cylindrical or cup-shaped, as in corals. - -Porcelaneous—like porcelain. - -Pore—a very small opening. - -Posterior—situated behind; to the rear. - -Precambrian—that portion of geologic time before the Cambrian; divided - into Archeozoic era (Early Precambrian) and Proterozoic era (Late - Precambrian). - -Protero—combining form meaning fore, former, or anterior in time (Greek - _proteros_, fore). - -Proterozoic—youngest era of the Precambrian; follows the Archeozoic era - and precedes the Cambrian period of the Paleozoic era. - -Protista—the organic kingdom including the simplest of all one-celled - organisms which possess various characters of both plants and animals; - bacteria, algae, foraminifers, radiolarians. - -Protoconch—in mollusks, the initial chamber of shell. - -Pyrite—a hard, brass-yellow mineral composed of iron sulfide; “fool’s - gold.” - -Quaternary—the youngest period of the Cenozoic era, follows the Tertiary - period. - -Radial symmetry—see Symmetry. - -Reef—a mound-like or ridge-like elevation of the sea bottom which almost - reaches the surface of the water, composed primarily of organic - material and commonly formed by reef-building animals, such as corals - and oysters. - -Replacement—type of fossilization whereby hard parts of organisms are - removed by solution accompanied by almost simultaneous deposition of - other substances in the resulting voids; mineralization. - -Respiration—the process of oxygenation. - -Rock—an aggregation of one or more minerals. - -Rock-unit—divisions of rocks based on definite physical and lithologic - characteristics and not defined on the basis of geologic time alone; - groups, formations, members. - -Rudistid—a Cretaceous pelecypod that does not exhibit the typical clam - or oyster shape; many are cone-shaped, resembling corals. - -Saddle—in cephalopods, the forward flexure (curved toward the aperture) - of the suture or septum. - -Scaphopod—an exclusively marine mollusk with a single-valved tusk-shaped - shell; member of class Scaphopoda, phylum Mollusca. - -Scavenger—an animal that feeds on organic refuse. - -Sedentary—stationary in life, not moving from place to place. - -Sediment—material that has been deposited by settling from a - transportation agent such as water or air; typically composed of - weathered rock fragments. - -Sedimentary rock—rocks formed from the accumulation and lithification of - sediments. - -Segment—one of the parts into which a body naturally separates or is - divided; for example, segments of arthropods or annelid worms. - -Septal—pertaining to the septum. - -Septum (plural, septa)—a dividing wall or partition; in fusulinids, a - partition between chambers in the fusulinid shell; in corals, one of - the radiating, longitudinal, calcareous plates located within the - corallite; in cephalopods, the transverse partitions between the - chambers. - -Series—the rocks formed during an epoch; the time-stratigraphic term - next in rank below a system. - -Serrate—notched like a saw. - -Sessile—animal attached to the sea floor more or less permanently. - -Silica—an oxide of silicon (SiO₂). - -Siliceous—containing or pertaining to silica. - -Silicification—the process of combining or impregnating with silica. - -Silurian—the third oldest period of the Paleozoic era; follows the - Ordovician, precedes the Devonian. - -Sinus—an elongate depression on brachiopod shells. - -Siphuncle—in cephalopods, the segmented horny or calcareous tube which - extends from the protoconch to the living chamber. - -Slickensides—polished and grooved surfaces that are the result of two - rock masses sliding past each other as in faulting. - -Solitary—living alone; not part of a colony. - -Species—one of the smaller natural divisions in classification. - -Specific name—see Trivial name. - -Spicule—a minute spike or dart, skeletal element in sponges and - holothurians. - -Stratum (plural, strata)—a single bed or layer of rock. - -Strike—the direction of a real or imaginary line that is formed by the - intersection of a bed or stratum with a horizontal plane; strike is - perpendicular to the dip. - -Subconical—less than conical in shape; almost a cone. - -Suture—the line of junction between two parts; in crinoids, the line of - junction between two plates; in gastropods, the line of junction of - the whorls as seen on the exterior of the shell; in cephalopods, the - line of junction between a septum and the shell wall. - -Symmetry—orderly arrangement of parts of an object with reference to - lines, planes, or points. - -_Bilateral symmetry_—the symmetrical duplication of parts on each side - of a vertical anterior-posterior plane. - -_Radial symmetry_—the symmetrical repetition of parts around a common - vertical dorso-ventrally disposed axis. - -_Pentamerous symmetry_—symmetry arranged in a pattern of fives. - -System—the rocks formed during a period; the time-stratigraphic term - next in rank above a series. - -Taxonomy—that branch of science that deals with classification, - especially in relation to plants, animals, or fossils. - -Tertiary—the oldest period of the Cenozoic era; follows the Cretaceous - period of the Mesozoic and precedes the Quaternary period of the - Cenozoic. - -Test—the protective covering of some invertebrate animals. - -Theca—a sheath or case; in coelenterates, the bounding wall at or near - the margin of the exoskeleton; in echinoderms, the main body skeleton - (or calyx) which houses the animal’s soft parts; in graptolites, any - cup or tube of the colony. - -Thorax—in trilobites, that part of the body between the cephalon and - pygidium. - -Time-unit—a portion of continuous geologic time (e.g., eras, periods, - epochs, and ages). - -Time-rock unit—same as time-stratigraphic unit. - -Time-stratigraphic unit—term given to rock units with boundaries - established by geologic time; strata deposited during definite - portions of geologic time (e.g., systems, series, stages, etc.). - -Topography—the physical features or configuration of a land surface. - -Topographic map—a map showing the physical features of an area, - especially the relief and contour of the land. - -Transverse—at right angles to length. - -Triassic—the youngest period of the Mesozoic era; follows the Permian - period of the Paleozoic and precedes the Jurassic period of the - Mesozoic. - -Trilobite—an extinct marine arthropod having a flattened segmented body - covered by a hardened dorsal exoskeleton divided into three lobes. - -Trivial name—the Latinized name added to a generic name to distinguish - the species; same as specific name. - -Type locality—the geographic location at which a formation was first - described and from which it was named; or from which the type specimen - of a fossil species comes. - -Type specimen—the individual or specimen on which the original - designation of a species was established. - -Umbilicus—an external depression or opening at the center of many - loosely coiled shells; in gastropods it is usually located at the base - of the shell; in cephalopods it is usually located laterally. - -Umbo—the arched part of the valve near the beak in bivalve shells. - -Unicellular—composed of one cell. - -Valve—the one or more pieces comprising the shell of animals. - -Variety—a subdivision of a species, designated by a third name when a - variety is designated. - -Ventral—pertaining to the abdomen; as opposed to dorsal, pertaining to - the back. - -Vertebrate—an animal having a backbone or spinal column. - -Whorl—a single turn or volution of a coiled shell. - --zoic—combining form meaning “life” (Greek _zoikos_, life). - -Zooecium (plural, zooecia)—tube or chamber occupied by an individual of - the bryozoan colony; also called an autopore. - - - - - Footnotes - - -[1]Associate Professor of Geology, Lamar State College of Technology, - Beaumont, Texas. - -[2]Entries marked with asterisk are published by the Bureau of Economic - Geology, The University of Texas, Austin. Those not out of print are - distributed at nominal sale price; list sent on request. These - publications may be consulted at many public libraries and/or - Chamber of Commerce offices. - - - - - Index - - - Page numbers in italics indicate illustrations. - - - A - _Acanthoceras_: 77 - _Actinomma_: 49 - Africa: 87 - Agnatha: 87 - Alaska: 7 - _Alectryonia lugubris_: 68 - algae: 44, 46, 47 - “algal biscuits”: 44 - alligators: 95 - _Allorisma_: 67 - _Allosaurus_: 90, 97, 98 - Allotheria: 100 - allotherians: 100 - Amarillo College: 27 - amber: 7 - amblypods: 102 - _Ambocoelia_: 57 - _Amelanchier_: 48 - American Museum of Natural History: 2, 15, 96 - ammonites: 11, 75, 76, 77, 78 - Ammonoidea: 66 - ammonoids: 75, 76, 77, 78 - Amphibia: 89 - amphibians: 87, 92 - Amphineura: 56 - _Amphiscapha_: 61 - _Ancilla_: 64 - _Angulotreta_: 55, 56 - ankylosaurs: 90, 97, 99 - Annelida: 78 - annelids: 78 - _Anomia_: 74 - anteaters: 100 - Anthozoa: 49, 51 - _Apsotreta_: 55, 56 - aragonite: 11 - _Archelon_: 91 - _Archetectonica_: 64 - _Archaeopteryx_: 100 - Archeozoic, derivation and pronunciation: 33 - Archer County: 89 - _Archimedes_: 54 - _arietina, Exogyra_: 70 - Aristotle: 3 - Arizona: 7 - Arkansas: 37 - Arlington State College: 1, 27 - armadillos: 100, 102 - Aronow, Saul: 1 - Arthropoda: 78, 79, 80 - arthropods: 10, 78, 79, 80 - crustaceans: 79, 80 - insects: 7, 79 - ostracodes: 79, 80 - trilobites: 78, 80 - Articulata: 56 - Artiodactyla: 106 - artiodactyls: 106 - camels: 106 - entelodonts: 101, 106 - ash, volcanic: 5 - _Astacodes_: 79 - _Astartella_: 67 - Asteroidea: 82 - asteroids: 82, 83 - Asterozoa: 82 - _Astraeospongium_: 50 - _Astrhelia_: 53 - _Astylospongia_: 50 - _Aulosteges tuberculatus_: 12, 13 - Austin: 14, 17, 19, 87 - Austin College: 27 - Australia: 87 - author, of a fossil: 22 - autopores: 51 - Aves: 89, 100 - _Avonia_: 12, 13 - _signata_: 12, 13 - _subhorrida_: 12, 13 - - - B - bacteria: 47 - _Baculites_: 77 - bags, collecting: 17, 18 - Balcones fault zone: 36, 37 - baluchitheres: 104, 106 - _Baluchitherium_: 106 - _Barbatia_: 74 - Baylor County: 89 - Baylor University: 1, 2, 27, 90, 91, 95 - Beaumont: 1, 34 - clay: 34 - Beaver, Harold: 1 - _Belemnites_: 77, 78 - Belemnoidea: 78 - belemnoids: 77, 78 - _Bellerophon_: 61 - Big Bend area: 35, 36 - National Park: 35, 97, 102 - Big Spring: 89 - binomial nomenclature: 21-22 - Bird, R. T.: 2, 15, 96 - birds, fossil: 5, 100 - Blastoidea: 81 - blastoids: 26, 28, 81 - Blinn College: 27 - bone, permineralized: 9 - Books About Fossils: 108-110 - Boon, Jack: 1 - Brachiopoda: 54, 55, 56 - brachiopods: 26, 29, 54, 55, 56 - articulate: 54, 55, 56, 57, 58 - Cambrian: 55 - Cretaceous: 56 - inarticulate: 55, 56 - Mississippian: 55 - Pennsylvanian: 57, 58 - Permian: 12, 13 - Recent: 56 - silicified: 12, 13 - symmetry: 24, 26, 29 - _Brachiosaurus_: 90 - Brewster County: 11, 12, 35, 41 - brittle stars: 82 - Bronaugh, Richmond L.: 1 - Brontosaurus: 90, 97, 98 - _Brontotherium_: 104, 105, 106 - Brown, L. F., Jr.: 1 - Bryophyta: 44 - Bryozoa: 51, 54, 55 - bryozoans: 26, 27, 28, 30, 51, 54, 55, 84 - Mississippian: 54 - Pennsylvanian: 55 - _bulla, Venericardia_: 72 - Bureau of Economic Geology: 2, 19 - burrows: 14 - “button corals”: 49, 53 - - - C - _Calamites_: 48 - calcite: 10, 11 - callus: 59 - _Calyptraphorus_: 64 - _Camarotoechia_: 55 - Cambrian— - derivation and pronunciation: 34 - fossils: 40 - brachiopods: 55 - graptolites: 86 - of Franklin Mountains, Llano, Marathon, and Solitario uplifts: - 40 - camels: 106 - _cameratus, Neospirifer_: 58 - _Caninia_: 51, 52 - _Canis diris_: 102, 103 - _domestica_: 22 - caprinid: 27, 30 - caprock, of High Plains: 35 - carbon residues: 10, 86 - Carboniferous: 34 - _carinata, Ostrea_: 71 - Carnivora: 102 - carnivores: 102, 103 - _Caryocorbula_: 74 - _Caryocrinites_: 81 - Casey, Josephine: 2 - casts: 11 - catalog, fossil; number: 31 - cement, portland: 19 - Cenozoic— - derivation and pronunciation: 33 - periods of: 34 - rocks in Texas: 43 - central Asia: 106 - central Texas: 11, 42 - Cephalopoda: 56, 66, 75, 78 - cephalopods: 24, 26, 27, 28, 29, 30, 66, 75, 76, 77, 78 - ammonites: 75, 76, 77, 78 - ammonoids: 75, 76, 77, 78 - belemnoids: 77, 78 - ceratites: 75, 78 - coleoids: 77, 78 - cuttlefish: 78 - goniatites: 75, 76 - nautiloids: 66, 75, 76 - octopus: 66, 78 - squid: 66, 78 - sutures: 66, 75, 78 - ceratites: 75, 78 - ceratopsians: 90, 99, 100 - _Ceratosaurus_: 90 - _Cerithium_: 62 - chalicotheres: 104, 106 - Chelonia. _See_ turtles. - chisels: 17 - chitin: 10 - chitons: 56 - Chondrichthyes: 87 - _Chonetes_: 57 - Chordata: 84-102 - chordates: 84 - amphibians: 89, 92 - birds: 100 - fishes: 87, 88, 89 - graptolites: 40, 84, 86 - mammals: 100-107 - reptiles: 89-100 - _Cladochonus_: 51, 52 - _Cladophyllia_: 53 - clams: 11, 56, 59. _See also_ pelecypods. - class, taxonomic: 22 - classification, binomial nomenclature: 21-22 - units of: 22 - club mosses: 47 - coal: 20, 47 - mines: 20, 47 - plants: 16, 46, 47, 48 - _Cochlespiropsis_: 63 - Coelenterata: 49, 51, 84 - coelenterates: 49, 51-_53_ - Coleoidea: 66 - coleoids: 77, 78 - collecting bags: 17, 18 - columella, corals: 51 - gastropods: 59, 60 - columnal, crinoid: 81, 82, 83 - Comanchean series of Cretaceous: 34. _See also_ Lower Cretaceous. - compass: 19 - _Composita subtilita_: 57 - compound corals. _See_ corals, colonial. - concretions: 16 - coniferous trees: 7 - conodonts: 41, 88, 89 - _Conus_: 63 - Cooper, G. A.: 2, 12 - coprolites: 14 - corallite: 49, 51 - corallum: 51 - corals: 11, 24, 26, 27, 49, 51, 52, 53 - “button”: 49, 53 - colonial: 24, 27, 30, 51, 52, 53 - Cretaceous: 53 - “horn”: 49, 51, 52 - morphology: 51 - Pennsylvanian: 52 - polyp: 49 - solitary: 24, 28, 29, 30, 49, 51, 52, 53 - symmetry: 24, 26, 27, 28, 29, 30 - Tertiary: 53 - _Cordaites_: 48 - correlation: 32 - _Corythosaurus_: 90 - cotylosaurs: 89, 92 - crabs: 78, 79 - _Crassatella_: 72 - crayfish: 78 - creodonts: 102 - Cretaceous— - _See also_ Comanchean and Gulf series. - derivation and pronunciation: 34 - fossils: 42-43 - arthropods: 79 - brachiopods: 56 - cephalopods: 66, 67, 76, 77 - corals: 53 - crocodiles: 95, 96 - dinosaurs: 90, 91, 93, 94, 95, 97, 99 - echinoderms: 83, 84, 85 - foraminifers: 49 - gastropods: 59, 62 - nautiloids: 76 - pelecypods: 59, 66, 68-_71_ - shark teeth: 88 - worms: 78 - tubes: 9 - of central Texas, Edwards Plateau, Gulf Coastal Plain, High - Plains, north Texas, and Trans-Pecos Texas: 42 - “Pyrite Fossil Zone” of: 11 - crinoidal limestone: 41, 82, 83 - Crinoidea: 81 - crinoids: 26, 28, 41, 81, 82, 83 - calyx: 81, 82, 83 - morphology: 81 - stems: 26, 28, 81, 82, 83 - Crockett County: 42 - Crockett formation: 43 - crocodiles: 95, 96 - crossopterygians: 87 - crustaceans: 79, 80 - Culberson County: 35 - cuttlefish: 78 - cycads: 47, 48 - _Cymatoceras_: 75, 76 - Cystoidea: 81 - cystoids: 81, 82, 83 - - - D - “Dark Ages”: 3 - da Vinci, Leonardo: 3 - Davis, Darrell: 1 - Decapoda. _See_ Coleoidea. - deer: 106 - Del Mar College: 27 - dendrites: 14 - _Dendrograptus_: 86 - Denver, Colorado: 19 - _Derbya_: 57 - Devonian— - derivation and pronunciation: 34 - fossils: 41 - placoderms: 87, 88 - _Psilophyton_: 48 - of El Paso and Van Horn regions, Llano and Marathon uplifts: - 41 - Diablo Mountains: 41 - diatoms: 44, 46, 47 - Dibranchiata. _See_ Coleoidea. - _Dictyoclostus_: 55 - _Dimetrodon_: 92 - _Dinobastis_: 102, 103 - Dinocerata: 102 - dinocerates: 102, 105 - dinosaurs: 89, 90-_94_, 95, 96, 97, 98, 99, 100 - armored: 90, 97, 99, 100 - duck-billed: 90, 97, 99 - flying: 91, 94, 95 - horned: 90, 99, 100 - plate-bearing: 90, 97, 99 - swimming: 91, 93, 95 - _Diplodocus_: 90 - _Diplograptus_: 86 - dire wolf: 102, 103 - _diris, Canis_: 102, 103 - distillation: 10 - _Distorsio_: 63 - division, plant: 44 - Dixon, J. W., Jr.: 2, 90, 91 - dolomite: 11 - dolphins: 95 - _domestica, Canis_: 22 - DuBar, Jules: 1 - _Dufrenoyia_: 77 - - - E - Eastland County: 20 - East Texas State College: 27 - Echinodermata: 80-84 - echinoderms: 80-84 - asteroids: 82, 83 - blastoids: 81 - crinoids: 81, 82, 83 - cystoids: 81, 82, 83 - echinoids: 82, 84, 85 - holothuroids: 84 - sclerites: 83 - Echinoidea: 82 - echinoids: 26, 28, 29, 82, 84, 85 - Cretaceous: 84, 85 - plates: 84, 85 - spines: 84, 85 - Echinozoa: 82 - Edentata: 100 - edentates: 100, 101, 102 - Edwards Plateau: 19, 36, 37, 42, 43 - Egyptian desert: 3 - _Elasmosaurus_: 91 - elephants: 102 - Eleutherozoa: 82 - Ellison, Samuel P.: 1 - El Paso region— - Devonian of: 41 - Ordovician of: 40 - Precambrian of: 40 - Silurian of: 40 - _Endopachys_: 53 - _Enoploclytia_: 79 - entelodont: 101, 106 - _Eohippus._ _See_ _Hyracotherium_. - epoch, geologic: 33 - era, geologic: 33-34 - Erath County: 20 - _Eryops_: 92 - _Euomphalus_: 61 - _Euphemites_: 62 - Europe: 89 - _Exogyra arietina_: 70 - _laeviscula_: 70 - _ponderosa_: 70 - _texana_: 70 - - - F - “false fossils”: 14 - family, taxonomic: 22 - “feather stars”: 82 - ferns: 47, 48 - fish: 87, 88, 89 - armored: 41, 88 - carbon residue: 9 - scales: 10 - teeth: 10 - vertebrae: 10 - _Fistulipora_: 55 - _Flabellum_: 53 - foramen, pedicle: 54, 56 - Foraminifera: 47, 49 - Cretaceous: 49 - fusulinids: 26, 29, 49 - orbitoid: 26, 28 - Pennsylvanian: 49 - forams: 26, 28, 29, 47, 49 - formation, geologic: 34 - fossil— - birds: 5, 100 - burrows: 14 - cataloging: 31 - collecting: 17 - equipment: 17 - ethics: 20 - how to collect: 20 - where to look: 19 - definition: 3 - dung: 14 - footprints: 14 - gizzard stone: 14 - identification: 21, 23-30 - keys: 26-30 - preservation— - altered hard parts: 10-11 - carbonization: 9, 10 - mineralization: 10 - permineralization: 10 - petrifaction: 10 - replacement, calcareous, iron, siliceous: 10, 11, 13 - kinds of: 7 - original hard and soft parts: 7 - record, missing pages in: 5 - wood: 47 - fossilization, requirements of: 5 - fossils— - animal: 47-107 - Cambrian: 40 - carbonized: 10 - classification of: 21-22 - cleaning: 21 - etching in acid: 21 - frozen: 5, 7, 104 - guide and/or index: 32 - in amber: 7 - in oil saturated soil: 7 - in quicksand: 5 - in tar: 5 - in volcanic ash: 5 - main types of: 44 - natural mummies: 7 - permineralized or petrified: 10 - plant: 4, 10, 20, 32, 44-48 - Pleistocene: 101, 102, 103, 104 - Precambrian: 40 - preparation of: 21 - Quaternary: 43, 101, 102, 103, 104 - replaced or mineralized: 10 - silicified: 21 - Cretaceous: 11 - Permian: 11 - etching: 21 - Silurian: 40, 81 - Tertiary: 43 - Triassic: 42 - uses of: 31-32 - France: 106 - Franklin Mountains, Cambrian of: 40 - frogs: 89 - _Frondicularia_: 49 - fungi: 44 - Fusselman limestone: 40 - _Fusulina_: 49 - fusulinids: 26, 29, 47, 49 - _Fusus_: 63 - - - G - Gaptank formation: 35, 41 - gastroliths: 14 - Gastropoda: 56, 59 - gastropods: 26, 27, 29, 30, 56, 59, 60 - Cretaceous: 59, 62 - morphology: 60 - ornamentation: 59 - Pennsylvanian: 61, 62 - Tertiary: 59, 63, 64 - generic name: 21-22 - genus: 21-22 - geologic— - column: 33 - history: 33 - map, definition: 40 - map of Texas: 38-39 - time: 34 - time scale: frontispiece, 33 - geology of Texas: 37-43 - Germany: 5, 100 - _Gingko_: 47, 48 - _Girtyocoelia_: 50 - Glasscock County: 42 - Glass Mountains: 11, 12, 35, 41, 42 - glauconite: 11 - _Globigerina_: 49 - Glossary: 111-114 - _Glycymeris_: 74 - _Glyptodon_: 101, 102 - glyptodont: 101, 102 - goats: 106 - goniatites: 75, 76 - Grand Prairie: 36, 37 - Graptolithina: 84, 86 - graptolites: 27, 30, 40, 84, 86 - of Marathon uplift: 40, 86 - Graptozoa. _See_ graptolites. - _graysonana, Gryphaea_: 69 - Great Flood: 3 - ground sloths: 7, 101, 102 - _Gryphaea graysonana_: 69 - _washitaensis_: 69 - Guadalupe Mountains, Peak: 35 - Gulf Coast: 32 - Gulf Coastal Plain of Texas: 35, 36, 37, 42, 43, 106 - Gulf of Mexico: 37 - Gulf series of Cretaceous: 34. _See also_ Upper Cretaceous. - _Gyrodes_: 62 - - - H - hagfish: 87 - hammer, geologist’s: 17, 18 - _Hamulus_: 78 - hand lens: 17, 18 - hard parts, animal—calcareous, chitinous, phosphatic, siliceous - remains: 10 - Hardin-Simmons University: 27 - heart urchins: 82, 83 - _Heliospongia_: 50 - hematite: 11 - _Hemiaster_: 85 - Hemichordata: 84 - Henderson County Junior College: 27 - Herodotus: 3 - _Heterostegina_: 32 - _Heteralosia hystricula_: 12, 13 - “het” zone: 32 - Hexacoralla: 51 - High Plains: 35, 36, 37, 42, 43, 89, 95, 106 - hippopotamuses: 106 - _Holaster_: 85 - _Holectypus_: 85 - Holothuroidea: 82 - holothuroids: 84 - sclerites: 83 - _Homo sapiens_: 22 - “horn corals”: 49, 51, 52 - horses: 103, 104 - teeth: 104 - Howard County Junior College: 27 - Hudspeth County: 35, 41, 42 - Hueco Mountains: 41 - Hughes, Jack T.: 1 - hydroids: 49 - Hydrozoa: 49, 84 - _Hyracotherium_: 103, 104 - _hystricula, Heteralosia_: 12, 13 - - - I - ichthyosaurs: 91, 93, 95 - _Ichthyosaurus_: 91, 93 - identification keys, fossil: 26-30 - use of: 23-27 - igneous rocks: 5, 19 - Inarticulata: 54, 56 - _Inoceramus_: 69 - insects: 7, 78, 79 - in amber: 7 - iron, replacement by: 11 - Italy: 3 - - - J - Jack County: 20 - jellyfish: 5, 49 - Jurassic— - derivation and pronunciation: 34 - fossils: 42 - birds: 100 - dinosaurs: 90, 91, 95, 97, 98, 99 - _Gingko_: 48 - of Hudspeth County and/or Malone Mountain: 41 - _Juresania_: 58 - - - K - keys. _See_ identification keys. - Kilgore College: 27 - _Kingena wacoensis_: 56 - - - L - labels, paper: 19 - _laeviscula, Exogyra_: 70 - Lamar State College of Technology: 1, 2, 27 - lampreys: 87 - _Latirus_: 63 - Lee College: 27 - _Lepidodendron_: 46 - _Levifusus_: 64 - _Lima_: 72 - limonite: 11 - _Lingula_: 55, 56 - Linnaeus: 21 - Linné: 21 - _Linoproductus_: 57 - _lisbonensis, Ostrea_: 72 - liverworts: 44 - lizards: 89 - Llano uplift: 36, 37, 40, 41 - Lonsdale, John T.: 1 - lophophore, brachiopod: 54 - _Lophophyllidium_: 49, 51, 52 - _proliferum_: 52 - _radicosum_: 52 - Los Angeles, California: 5 - Louisiana: 37 - Lower Cretaceous: 34, 42, 56, 97. _See also_ Comanchean. - _lugubris, Alectryonia_: 68 - _Lunatia_: 62 - lungfishes: 87 - - - M - Macon, J. W.: 2 - magnifying glass: 17, 18 - Malone Mountain: 42 - Mammalia: 89, 100-107 - mammoths: 102, 104, 107 - frozen: 7, 102 - tooth: 104 - woolly: 102, 104, 107 - mantle, brachiopod: 54 - pelecypod: 59 - maps— - county: 17 - geologic: 19 - of Texas: 38-39 - physiographic of Texas: 36 - topographic: 19, 20 - Marathon uplift: 35, 36, 40, 41 - marcasite: 11 - _Marginifera_: 57 - _opima_: 12, 13 - mastodon, tooth: 104 - _Meandrostia_: 50 - Mediterranean Sea: 3 - _mercenaria, Venus_: 22 - _Mesalia_: 63 - _Mesolobus_: 57 - Mesozoic— - derivation and pronunciation: 33 - periods of: 34 - rocks in Texas: 42-43 - metamorphic rocks: 5, 19 - _Metoicoceras_: 76 - _Michelinia_: 52 - _Micrabacia_: 49, 52 - microfossils: 4, 10, 32, 47, 49, 50, 78 - micropaleontological slides: 32 - micropaleontologist: 32, 47, 80 - micropaleontology: 4, 89 - Midwestern University: 27 - mine dumps: 20, 47 - Mississippian— - derivation and pronunciation: 34 - fossils: 41 - blastoid: 81 - brachiopods: 55 - bryozoan: 54 - of Hueco Mountains: 41 - of Llano region: 41 - mold, external: 9, 11, 59, 66 - internal: 9, 11, 59, 62, 66 - Mollusca: 56-78 - mollusks: 7, 56, 59-78. _See also_ Mollusca. - _Moropus_: 106 - mosasaur: 91, 93, 95 - “moss animals”: 54 - mosses: 44 - _Muirwoodia multistriatus_: 12, 13 - multituberculates: 100 - _multistriatus, Muirwoodia_: 12, 13 - mussels: 56, 59 - museums, as aid in identification: 23 - American, Natural History: 2, 15, 96 - Strecker: 95 - Texas Memorial: 14, 87, 95, 97, 100, 102 - _Myalina_: 67 - _Mylodon_: 100, 101 - - - N - Nautiloidea: 66 - nautiloids: 66 - Cretaceous: 76 - morphology: 75 - Pennsylvanian: 76 - sutures: 75 - _Nautilus_: 66 - morphology: 75 - _Neithea_: 70 - _Neospirifer_: 57 - _cameratus_: 58 - _Nerinea_: 62 - _Neuropteris_: 48 - _Neverita_: 64 - New Mexico: 7 - New York City: 14 - North-Central Plains: 35, 36, 37, 40, 41, 42, 43 - north Texas: 42 - North Texas State College: 27 - notebook, field: 17 - _Notopocorystes_: 79, 80 - _Nucula_: 73 - _Nuculana_: 67 - _Nuculopsis_: 67 - - - O - octopus: 66, 78 - Odessa College: 27 - operculum: 59 - _Ophiuroidea_: 82 - ophiuroids: 82 - _opima, “Marginifera”_: 12, 13 - order, taxonomic: 22 - Ordovician— - derivation and pronunciation: 34 - fossils: 40 - graptolites: 86 - of El Paso region, Llano, Marathon, Solitario, and Van Horn - uplifts: 40 - ornamentation, brachiopod: 54 - gastropod: 59 - pelecypod: 66 - Ornithischia: 97 - ornithischians: 90, 97, 98, 100 - Ornithopoda: 97 - ornithopods: 90, 97, 99 - _Orthoceras_: 66, 76 - _Orthoyoldia_: 73 - ossicles. _See_ sclerites. - _Osteichthyes_: 87 - Ostracoda: 80 - ostracoderms: 87 - ostracodes: 78, 79, 80 - _Ostrea carinata_: 71 - _lisbonensis_: 72 - _quadriplicata_: 71 - _sellaeformis_: 72 - _Oxytropidoceras_: 77 - oysters: 56, 59 - - - P - _Pachecoa_: 72 - _Pachymya_: 71 - paleobotany: 4 - paleobotanists: 44 - paleontology— - definition: 4 - divisions of: 4 - history of: 3 - invertebrate: 4 - vertebrate: 4 - _Paleoscincus_: 90, 97, 99, 100 - Paleozoic— - derivation and pronunciation: 33 - periods of: 34 - rocks of Texas: 40-42 - Palo Pinto County: 20 - Paluxy Creek: 14, 15 - Pan American College: 27 - Pantodonta: 102 - pantodonts: 102 - _Parasaurolophus_: 90 - _Parasmilia_: 53 - Parker County: 20 - Pawpaw formation: 11 - pearly nautilus: 66 - morphology: 75 - Pecos County: 42 - Pecos River valley: 35 - _Pecten_: 59, 68, 74 - pedicle: 54, 56 - foramen: 54, 56 - valve, brachiopod: 54 - Pelycosaurs: 89, 92 - Pelecypoda: 56, 59, 65-66 - pelecypods: 26, 29, 30, 56, 59, 60, 66 - Cretaceous: 59, 66, 68-_71_ - dentition: 66 - morphology: 59, 60, 65, 66 - ornamentation: 66 - Pennsylvanian: 66, 67 - teeth: 60, 65, 66 - Tertiary: 72, 73, 74 - Pelmatozoa: 80, 81 - Pennsylvanian— - derivation and pronunciation: 34 - fossils: 41 - brachiopods: 57, 58 - bryozoans: 55 - cephalopods: 66, 76 - corals: 52 - crinoids: 41, 82, 83 - fusulinids: 47, 49 - gastropods: 61, 62 - nautiloids: 76 - pelecypods: 66, 67 - plants: 46, 47, 48 - shark teeth: 87 - sponges: 50 - of Diablo and Hueco Mountains, Llano and Marathon uplifts, and - north-central Texas: 41 - _Pentaceros_: 83 - _Pentagonaster_: 83 - _Pentremites_: 81 - period, geologic: 33 - periostracum: 60 - Perissodactyla: 104 - perissodactyls: 103, 104, 105 - Permian— - derivation and pronunciation: 34 - fossils: 41 - amphibian: 89, 92 - brachiopods: 12, 13 - cotylosaurs: 89, 92 - pelycosaurs: 89, 92 - of Glass Mountains: 11, 12, 35 - _permiana, Prorichthofenia_: 12, 13 - permineralized bone: 9 - petroleum geologist: 4 - _Phaneroceras_: 76 - _Phobosuchus_: 95, 96 - _Pholadomya_: 71, 72 - phyla: 22 - _Phyllograptus_: 86 - phylum: 22 - physiographic provinces, of Texas: 35-37 - physiography, definition: 35 - of Texas: 35-37 - phytosaurs: 42, 91, 94, 95 - pick, mineralogist’s or prospector’s: 17, 18 - pigs: 106 - _Pinna_: 67 - Pisces: 86-89 - _Pitar_: 72 - Placodermi: 87 - placoderms: 87, 88 - plant kingdom: 44 - plants, classification: 44 - Pennsylvanian: 46, 47, 48 - _Platyceras_: 62 - Pleistocene: 43. _See also_ Quaternary. - fossils: 101, 102, 103, 104 - plesiosaurs: 91, 93, 95 - _Pleurocora_: 53 - _Plicatula_: 68, 74 - _Pliohippus_: 103 - Poland: 7, 106 - pollen: 47 - polyp, coral: 49 - _Polypora_: 55 - _ponderosa, Exogyra_: 70 - Porifera: 49 - _Porodiscus_: 49 - portland cement: 19 - Precambrian— - definition: 34 - fossils: 40 - of El Paso region: 40 - of Llano uplift: 37, 40 - of Van Horn uplift: 40 - rocks of Texas: 40 - Presidio County: 35 - Proboscidea: 102 - proboscideans: 102, 104, 107 - teeth: 104 - _proliferum, Lophophyllidium_: 52 - _Prorichthofenia permiana_: 12, 13 - Proterozoic, derivation and pronunciation: 33 - Protista: 47 - _Protocardia_: 68 - _Protoceratops_: 90 - Protozoa: 47, 49 - protozoans: 47 - pseudofossils: 14 - _Pseudoliva_: 63 - _Psilophyton_: 48 - _Pteranodon_: 91, 94 - Pterodactyloids: 91 - pterosaurs: 91, 94, 95 - _Punctospirifer_: 57 - pyrite: 11 - “Pyrite Fossil Zone” of Cretaceous: 11 - - - Q - _quadriplicata, Ostrea_: 71 - quarries: 19 - Quaternary— - derivation and pronunciation: 34 - fossils: 43, 101, 102, 103, 104 - of Edwards Plateau, Gulf Coast, High Plains, North-Central - Plains, and Trans-Pecos Texas: 43 - quicksand: 5 - - - R - _radicosum, Lophophyllidium_: 53 - Radiolaria: 47 - radiolarians: 47, 49 - Rancho La Brea tar pit: 5 - rays: 87 - Reagan County: 42 - _Receptaculites_: 50 - Renaissance: 3 - Reptilia: 89-100 - reptiles: 89-100 - rhamphorhynchoids: 91 - _Rhamphorhynchus_: 91, 94 - rhinoceroses: 7, 104, 106, 107 - woolly: 106, 107 - _Rhipodomella_: 55 - _Rhombopora_: 51, 55 - Rice University: 27 - Rio Grande valley, of Trans-Pecos: 35, 95 - road metal: 19 - _Robulus_: 49 - Rock and Mineral Clubs: 23 - rock units: 34 - _rockymontanus, Spirifer_: 58 - Rodda, Peter U.: 1 - rudistids: 26, 27, 28, 29, 30 - Rugosa: 51 - - - S - saber-tooth cat: 102, 103 - St. Mary’s University: 27 - salamanders: 89 - _Salenia_: 85 - San Angelo College: 27 - San Antonio College: 27 - sand dollars: 82 - _sapiens, Homo_: 22 - Sarcodina: 47 - Saurischia: 97 - saurischians: 90, 97, 99 - Sauropoda: 97 - sauropods: 90, 97, 98 - scale trees: 46, 47 - scallops: 56, 59 - Scaphopoda: 56 - scaphopods: 26, 27, 28, 29, 56 - _Schizodus_: 67 - scientific names: 21-23 - Scleractinia: 51 - sclerites, holothurian: 83, 84 - scolecodont: 78 - scouring rushes: 47, 48 - Scyphozoa: 49, 84 - sea anemones: 49 - sea cucumbers: 82 - “sea lily”: 81, 82 - “sea mats”: 51, 54 - “sea-mice”: 56 - sea urchins: 82 - sedimentary rocks: 5, 19 - _sellaeformis, Ostrea_: 72 - septa, cephalopods: 66, 75 - corals: 49, 51 - serpent stars: 82 - _Serpula_: 78 - _Seymouria_: 92 - sharks: 87 - teeth: 10, 87, 88 - sheep: 106 - shrimp: 78 - Siberia: 7, 106 - _Sigillaria_: 46 - _signata, Avonia_: 12, 13 - silica: 10, 11 - silicification: 11 - Silurian— - derivation and pronunciation: 34 - fossils: 40 - cystoid: 81 - of El Paso and Van Horn regions: 40 - skates: 87 - slickensides: 16 - slugs: 56 - Smith, Fred: 1 - snails: 11, 56, 59. _See also_ gastropods. - snakes: 89 - Solitario uplift: 40 - Somervell County: 14, 15 - South America: 87, 102 - Southern Methodist University: 27 - South Texas College: 27 - Southwestern University: 27 - species: 22 - spicules, sponge: 49, 50 - spiders: 78 - spines, echinoid: 84, 85 - _Spirifer rockymontanus_: 58 - _Spirorbis_: 78 - sponges: 10, 27, 30, 49, 50 - spores: 47 - _Squamularia_: 57 - squid: 66, 78 - starfish: 82, 83 - _Stegosaurus_: 90, 97, 99 - stegosaurs: 90, 97, 99 - steinkern: 59, 62 - stems, crinoid: 26, 28, 41, 81, 82, 83 - Stephen F. Austin State College: 27 - “stomach stones”: 14 - stone, building: 19 - Strabo: 3 - _Straparolus_: 61 - Strecker Museum: 95 - _Striatopora_: 51, 52 - _Strobeus_: 62 - Styracosaurus: 90 - _subhorrida, Avonia_: 12, 13 - _subtilita, Composita_: 57 - Sul Ross State College: 27 - _Surcula_: 64 - sutures, cephalopod: 66, 75, 78 - nautiloid: 75 - swine, giant: 106 - _Sycostoma_: 64 - symmetry: 23 - bilateral: 24, 26, 29 - radial: 24, 26, 28, 80 - - - T - tabulae: 51 - Tabulata: 51 - tape, masking: 19 - tapirs: 104 - tar: 5 - Tarleton State College: 27 - Tarrant County: 11 - taxonomy: 21-22 - teeth, horse: 104 - mammoth: 104 - shark: 10, 87, 88 - _Tellina_: 73 - Tertiary— - derivation and pronunciation: 34 - fossils: 43 - corals: 53 - gastropods: 59, 63, 64 - mammals: 100-107, 103, 105 - microfossils: 32 - pelecypods: 72, 73, 74 - radiolarians: 49 - rocks of Gulf Coastal Plain, High Plains, North-Central - Plains, and Trans-Pecos region: 42 - Tetracoralla: 51 - Tetrapoda: 86, 89-107 - _texana, Exogyra_: 70 - _Texanites_: 77 - Texas A. & M. College: 1, 27 - Texas Christian University: 27 - Texas College: 27 - Texas College of Arts and Industries: 27 - Texas Highway Department: 17 - Texas Memorial Museum: 14, 87, 95, 97, 100, 102 - Texas Technological College: 27 - Texas, the geology of: 34, 37-43 - Texas Western College: 27 - Thallophyta: 43, 46 - Theophrastus: 3 - Therapsids: 89 - Theria: 100 - therians: 100-107 - artiodactyls: 101, 106 - carnivores: 102, 103 - dinocerates: 102, 105 - edentates: 100, 101, 102 - pantodonts: 102 - perissodactyls: 104 - proboscideans: 102, 104, 107 - Theropoda: 97 - theropods: 90, 97, 98 - The University of Texas: 1, 2, 27 - time, geologic: 34 - titanotheres: 104, 105, 106 - toads: 89 - tortoises: 89 - traces of organisms: 14 - burrows: 14 - coprolites: 14 - gastroliths: 14 - tracks: 14, 15 - trails: 14 - Tracheophyta: 44, 46, 48 - _Trachodon_: 90, 97, 99 - tracks, dinosaur: 14, 15, 97 - Trans-Pecos region: 35, 36, 40, 42, 43, 86, 95, 102, 106 - tree sloths: 100, 102 - trees, coniferous: 7 - _Trepospira_: 61 - Triassic— - derivation and pronunciation: 34 - fossils: 42 - dinosaurs: 95 - phytosaurs: 91, 94, 95 - of Crockett, Glasscock, Pecos, Reagan, and Upton counties; - Glass Mountains and High Plains: 42 - _Triceratops_: 90, 99, 100 - _Trigonia_: 69 - Trilobita: 78 - trilobites: 78, 80 - morphology: 80 - Trilobitomorpha: 78 - _Trinacromerum_: 91 - Trinity University: 27 - trivial name: 21-22 - _Trochosmilia_: 53 - _Tuba_: 64 - _tuberculatus, Aulosteges_: 12, 13 - _Turrilites_: 77 - _worthensis_: 22 - _Turritella_: 62, 63 - turtles: 89, 91 - tusk-shells: 56 - Tyler Junior College: 27 - _Tylosaurus_: 91, 93 - _Tylostoma_: 62 - _Tyrannosaurus_: 90, 97 - - - U - uintatheres: 102, 105 - _Uintatherium_: 102, 105 - umbilicus: 59, 60 - United States Geological Survey: 19 - United States National Museum: 2, 12 - University of Corpus Christi: 27 - University of Houston: 1, 27 - University of Texas, The: 1, 2, 27 - Upper Cretaceous: 34, 42, 78. _See also_ Gulf. - Upton County: 42 - - - V - valves, brachiopod: 54, 56 - pelecypod: 59, 65, 66 - Van Horn uplift: 35, 36, 40, 41 - _Venericardia_: 73 - _bulla_: 72 - ventral valve, brachiopod: 54 - _Venus mercenaria_: 22 - _Vertagus_: 63 - Vertebrata: 84, 86-107 - vertebrates: 86-107 - amphibians: 89, 92 - birds: 100 - fish: 87, 88, 89 - mammals: 100-107 - reptiles: 89-100 - _Vokesula_: 73 - volcanic ash: 5 - _Volutolithes_: 64 - - - W - Waco: 91, 92, 95 - _wacoensis, Kingena_: 56 - Washington, D. C.: 19 - _washitaensis, Gryphaea_: 69 - Weches formation: 43 - West Texas State College: 1, 27 - Wilson, John A.: 2 - Wilson, Sarah Louise: 2 - Wise County: 20 - wood, petrified: 19 - Woodbine: 10, 37, 47 - worms, annelid, fossil, segmented: 78 - worm tubes, Cretaceous: 9 - _Worthenia_: 61 - _worthensis, Turrilites_: 22 - - - Y - _Yoldia_: 67 - Young County: 20 - Young, Keith: 1 - - - Z - Zoantharia: 51 - zooecia: 51 - - - - - Transcriber’s Notes - - ---Retained publication information from the printed edition: this eBook - is public-domain in the country of publication. - ---Corrected a few palpable typos. - ---Included a transcription of the text within some images. - ---In the text versions only, text in italics is delimited by - _underscores_. - - - - - - - -End of the Project Gutenberg EBook of Texas Fossils: An Amateur Collector's -Handbook, by William H. 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