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diff --git a/30297-0.txt b/30297-0.txt new file mode 100644 index 0000000..2d23fec --- /dev/null +++ b/30297-0.txt @@ -0,0 +1,398 @@ +*** START OF THE PROJECT GUTENBERG EBOOK 30297 *** + +UNIVERSITY OF KANSAS PUBLICATIONS + +MUSEUM OF NATURAL HISTORY + +Volume 14, No. 17, pp. 483-491, 2 figs. +March 2, 1964 + + +Records of the Fossil Mammal +Sinclairella, Family Apatemyidae, +From the Chadronian and Orellan + + +BY + +WILLIAM A. CLEMENS, JR. + + +UNIVERSITY OF KANSAS +LAWRENCE +1964 + + +UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY + +Editors: E. Raymond Hall, Chairman, Henry S. Fitch, +Theodore H. Eaton, Jr. + +Volume 14, No. 17, pp. 483-491, 2 figs. +Published March 2, 1964 + +UNIVERSITY OF KANSAS +Lawrence, Kansas + +PRINTED BY +HARRY (BUD) TIMBERLAKE, STATE PRINTER +TOPEKA, KANSAS + +1964 + + +29-8587 + + + + +Records of the Fossil Mammal +Sinclairella, Family Apatemyidae, +From the Chadronian and Orellan + +BY + +WILLIAM A. CLEMENS, JR. + + +Introduction + + +The family Apatemyidae has a long geochronological range in North +America, beginning in the Torrejonian land-mammal age, but is +represented by a relatively small number of fossils found at a few +localities. Two fossils of Orellan age, found in northeastern Colorado +and described here, demonstrate that the geochronological range of the +Apatemyidae extends into the Middle Oligocene. Isolated teeth of +_Sinclairella dakotensis_ Jepsen, part of a sample of a Chadronian +local fauna collected by field parties from the Webb School of +California, are also described. + + I thank Mr. Raymond M. Alf, Webb School of California, + Claremont, California, and Dr. Peter Robinson, University of + Colorado Museum, Boulder, Colorado, for permitting me to + describe the fossils they discovered. Also Dr. Robinson made + available the draft of a short paper he had prepared on the + tooth found in Weld County, Colorado; his work was + facilitated by a grant from the University of Colorado + Council on Research and Creative Work. I also gratefully + acknowledge receipt of critical data and valuable comments + from Drs. Edwin C. Galbreath, Glenn L. Jepsen, and Malcolm + C. McKenna who is currently revising the Paleocene + apatemyids and studying the phylogenetic relationships of + the family. The prefixes of catalogue numbers used in the + text identify fossils in the collections of the following + institutions: KU, Museum of Natural History, The University + of Kansas, Lawrence; Princeton, Princeton Museum, Princeton, + New Jersey; RAM-UCR, Raymond Alf Museum, Webb School of + California, Claremont, California (the permanent repository + for these specimens will be the University of California, + Riverside); and UCM, University of Colorado Museum, Boulder, + Colorado. The system of notations for teeth prescribed for + use here is as follows: teeth in the upper half of the + dentition are designated by a capital letter and a number; + thus M2 is the notation for the upper second molar; teeth in + the lower half of the dentition are designated by a + lower-case letter and a number; thus p2 is the notation for + the lower second premolar. + + + + +Family APATEMYIDAE Matthew, 1909 + +Genus =Sinclairella= Jepsen, 1934 + +=Sinclairella dakotensis= Jepsen, 1934 + + +The type of the species, Princeton no. 13585, was discovered in +Chadronian strata of the upper part of the Chadron Formation cropping +out in Big Corral Draw, approximately 13 miles south-southwest of +Scenic, in southwestern South Dakota (Jepsen, 1934, p. 291). Detailed +descriptions of the type specimen are given in papers by Jepsen (1934) +and Scott and Jepsen (1936). Isolated teeth of Chadronian age referable +to _Sinclairella dakotensis_ have been discovered subsequently at a +locality in Nebraska and fossils of Orellan age, also referable to _S. +dakotensis_, have been collected at two localities in Colorado. The +sample from each locality is described separately. + + +Sioux County, northwestern Nebraska + + _Material._--RAM-UCR nos. 381, left M1; 598, left m2; 1000, + right m1; 1001, right m2; 1079, right m2; 1674, right M2; + and 3013, left m2. + + _Locality and stratigraphy._--These Chadronian fossils were + discovered by Raymond Alf and members of his field parties + in several harvester ant mounds built in exposures of the + Chadron Formation in Sec. 26, T 33 N, R 53 W, Sioux County, + Nebraska (Alf, 1962, and Hough and Alf, 1958). This is UCR + locality V5403. The collectors carefully considered the + possibility that some of the fossils found in the ant mounds + were collected from younger strata by the harvester ants and + concluded this was unlikely (Alf, personal communication). + + _Description and comments._--The cusps of RAM-UCR no. 381, a + left M1, are sharp and the wear-facets resulting from + occlusion with the lower dentition are small. The paraconule + is a low, ill-defined cusp on the anterior margin of the + crown; a metaconule is not present. A smooth stylar shelf is + present labial to the metacone. The crown was supported by + three roots. There are no interradicular crests. + + The crown of RAM-UCR no. 1674, a right M2, is heavily + abraded and many morphological details of the cusps have + been destroyed. Low interradicular crests linked the three + roots of the tooth with a low, central prominence. As was + the case with RAM-UCR no. 381, no significant differences + could be found in comparisons with illustrations of the + teeth preserved in Princeton no. 13585. + + RAM-UCR nos. 598, 1001, 1079, and 3013 all appear to be + m2's. The talonids of these teeth are not elongated, their + trigonids have quadrilateral outlines, and the paraconids + are small but prominent, bladelike cusps. The trigonid of + RAM-UCR 1000 is elongated and the paraconid is a minute + cusp; the tooth closely resembles the m1 of the type of + _Sinclairella dakotensis_. + + +Logan County, northeastern Colorado + + _Material._--KU no. 11210 (fig. 1), a fragment of a left + maxillary containing P4 and M1-2. + + _Locality and stratigraphy._--The fossil was found in the + center of the W-1/2, Sec. 21, T 11 N, R 53 W, Logan County, + Colorado, "... in the bed below _Agnotocastor_ bed, Cedar + Creek Member...." (Ronald H. Pine, 1958, field notes on file + at the University of Kansas). The bed so defined is part of + unit 3 in the lower division of the Cedar Creek Member, as + subdivided by Galbreath (1953:25) in stratigraphic section + XII. The fauna obtained from unit 3 is of Orellan age. + +[Illustration: FIG. 1. _Sinclairella dakotensis_ Jepsen, KU no. 11210, +fragment of left maxillary with P4 and M1-2; Orellan, Logan County, +Colorado; drawings by Mrs. Judith Hood: a, labial view; b, occlusal +view; both approximately × 9.] + + _Description and comments._--P4 of KU no. 11210 has a large + posterolingual cusp separated from the main cusp by a + distinct groove, which deepens posteriorly. The + posterolingual cusp is supported by the broad posterior + root. P4 of the type specimen of _Sinclairella dakotensis_ + is described (Jepsen, 1934, p. 392) as having an oval + outline at the base of the crown, and a small, + posterolingual cusp. A chip of enamel is missing from the + posterior slope of the main cusp of the P4 of KU no. 11210. + The anterior slope of the main cusp is flattened, possibly + the result of wear, and there is no evidence of a groove + like that present on the P4 of the type specimen. + + Only a few differences were found between the molars + preserved in KU no. 11210 and their counterparts in the type + specimen. A stylar shelf is present labial to the metacone + of M1 of KU no. 11210, but, unlike the type, its surface is + smooth and there is no evidence of cusps. Of the three small + stylar cusps on the stylar shelf of M2 the smallest is in + the position of a mesostyle. The M2 lacks a chip of enamel + from the lingual surface of the hypocone. Unlike the M2 of + Princeton no. 13585, in occlusal view the posterior margin + of the M2 of KU no. 11210 is convex posterior to the + metacone. The anterior edge of the base of the zygomatic + arch of KU no. 11210 was dorsal to M2. The shallow oval + depression in the maxillary dorsal to M1 might be the result + of post-mortem distortion. + + The molars preserved in KU no. 11210 and their counterparts + in the type specimen do not appear to be significantly + different in size (table 1) or morphology of the cusps. The + only difference between the two specimens that might be of + classificatory significance is the difference in size of the + posterolingual cusp of P4. At present the range of + intraspecific variation in the morphology of P4 has not been + documented for any species of apatemyid. The evolutionary + trend or trends of the apatemyids (McKenna, 1960, p. 48) for + progressive reduction of function of p4 probably were + paralleled by similar trends in the evolution of the P4. If + so, the intraspecific variation in the morphology of P4 + could be expected to be somewhat greater than that of the + upper molars, for example. The morphological difference + between the P4's of the type of _Sinclairella dakotensis_ + and KU no. 11210 is not extreme and does not exceed the + range of intraspecific variation that could be expected for + this element of the dentition. The close resemblances in + size and morphology between the M1-2 of Princeton no. 13585 + and KU no. 11210 also favor identification of the latter as + part of a member of an Orellan population of _Sinclairella + dakotensis_. + + +Weld County, northeastern Colorado + +[Illustration: FIG. 2. _Sinclairella dakotensis_ Jepsen, UCM no. 21073, +right M2; Orellan, Weld County, Colorado; drawing by Mrs. Judith Hood: +occlusal view, approximately × 9.] + + _Material._--UCM no. 20173 (fig. 2), is a right M2. + + _Locality and stratigraphy._--The tooth was discovered at + the Mellinger locality, Sec. 17, T 11 N, R 65 W, Weld + County, Colorado. The Mellinger locality is in the Cedar + Creek Member, White River Formation, and its fauna is + considered to be of Orellan age (Patterson and McGrew, 1937, + and Galbreath, 1953). + + _Description and comments._--UCM no. 21073, which is more + heavily abraded than KU no. 11210, shows no evidence of a + stylar cusp either anterolabial to the metacone or in the + position of a mesostyle. A small stylar cusp is present + anterolabial to the paracone. A notch that appears to have + been cut through the enamel of the posterolabial corner of + the crown could have received the parastylar apex of M3. A + similar notch is not present on the M2 of KU no. 11210 nor + indicated in the illustrations of the M2 of Princeton no. + 13585. The coronal dimensions of UCM no. 21073 (table 1) do + not appear to differ significantly from those of the M2's of + KU no. 11210 and the type specimen of _Sinclairella + dakotensis_. + + +Comments + +With the discovery of Orellan apatemyids the geochronological range of +the family in North America is shown to extend from the Torrejonian +through the Orellan land-mammal ages. The discoveries reported here +enlarge the Oligocene record of apatemyids to include not only the type +specimen of _Sinclairella dakotensis_, a skull and associated mandible +from South Dakota, but also seven isolated teeth, representing at least +two individuals, from a Chadronian fossil locality in Nebraska and one +specimen from each of two Orellan fossil localities in northeastern +Colorado. Simpson (1944:73, and 1953:127) presented tabulations of the +published records of American apatemyids and suggested the data +indicated the populations of these mammals were of small size +throughout the history of the family. The few pre-Oligocene occurrences +of apatemyids described subsequently (note McKenna, 1960, figs. 3-10, +and p. 48) and occurrences described here tend to reinforce Simpson's +interpretation. This interpretation may have to be modified to some +degree, however, when current studies of collections of pre-Oligocene +apatemyids are completed (McKenna, personal communication). + +Although information concerning the evolutionary trends of American +apatemyids has been published, no data on the morphological variation +in a population are available in the literature. An adequate basis for +evaluating the significance of the morphological differences between +the P4's of Princeton no. 13585 and KU no. 12110 coupled with the +similarities of their M1-2's is lacking. In the evolution of American +apatemyids the P4 underwent reduction in size and, apparently, +curtailment of function. This history suggests the range of +morphological variation of P4 in populations of _Sinclairella +dakotensis_ could be expected to be greater than that of the molars and +encompass the morphological differences between the P4's of Princeton +no. 13585 and KU no. 12110. The difference in age of the Chadronian and +Orellan fossils does not constitute proof that they pertain to +different species. Although the identification is admittedly +provisional until more fossils including other parts of the skeleton +are discovered, the Orellan fossils described here are referred to +_Sinclairella dakotensis_. + + +TABLE 1.--MEASUREMENTS (IN MILLIMETERS) OF TEETH OF SINCLAIRELLA +DAKOTENSIS JEPSEN. + +========================================================================== + | P4 | M1 | M2 +-----------------------+------------+------------------+------------------ + |length|width|length[1]|width[1]|length[1]|width[1] +-----------------------+------+-----+---------+--------+---------+-------- +Princeton no. 13585[2] | 2.1 | 1.1 | 4.0 | 3.7 | 3.4 | 4.7 +RAM no. 381 | | | 4.1 | 3.5 | | +RAM no. 1674 | | | | | 3.4 | 4.2 +KU no. 11210 | 2.4 | 1.6 | 3.9 | 3.5 | 3.8 | 4.1+ +UCM no. 21073 | | | | | 3.6 | 4.1 +-----------------------+------+-----+---------+--------+---------+-------- + | m1 | m2 + +---------+--------+---------+-------- + | length | width | length | width + +---------+--------+---------+-------- +Princeton no. 13585[3] | 3.5 | 2.4 | 3.7 | 2.8 +RAM no. 1000 | 3.5 | 2.2 | | +RAM no. 598 | | | 3.8 | 2.6 +RAM no. 1001 | | | 3.6+ | 2.6 +RAM no. 1079 | | | 4.0 | 2.8 +RAM no. 3013 | | | 3.6 | 2.8 +------------------------------------+---------+--------+---------+-------- + +[Footnote 1: Length defined as maximum dimension of the labial half of +the crown measured parallel to a line drawn through the apices of +paracone and metacone. Width defined as maximum coronal dimension +measured along line perpendicular to line defined by apices of paracone +and metacone.] + +[Footnote 2: Dimensions provided by Dr. Glenn L. Jepsen.] + +[Footnote 3: Dimensions taken from Jepsen (1934:300).] + + + + +Literature Cited + +ALF, R. + 1962. A new species of the rodent _Pipestoneomys_ from the + Oligocene of Nebraska. Breviora, Mus. Comp. Zool., no. 172, + pp. 1-7, 3 figs. + +GALBREATH, E. C. + 1953. A contribution to the Tertiary geology and paleontology + of northeastern Colorado. Univ. Kansas Paleont. Cont., + Vertebrata, art. 4, pp. 1-120, 2 pls., 26 figs. + +HOUGH, J., and ALF, R. + 1958. A Chadron mammalian fauna from Nebraska. Journ. Paleon. + 30:132-140, 4 figs. + +JEPSEN, G. L. + 1934. A revision of the American Apatemyidae and the description + of a new genus, _Sinclairella_, from the White River + Oligocene of South Dakota. Proc. Amer. Philos. Soc., + 74:287-305, 3 pls., 4 figs. + +MCKENNA, M. C. + 1960. Fossil Mammalia from the early Wasatchian Four Mile fauna, + Eocene of northwest Colorado. Univ. California Publ. in + Geol. Sci., 37:1-130, 64 figs. + +MATTHEW, W. D. + 1909. The Carnivora and Insectivora of the Bridger Basin, Middle + Eocene. Mem. Amer. Mus. Nat. Hist., 9:289-567, pls. 42-52, + 118 figs. + +PATTERSON, B. and MCGREW, P. O. + 1937. A soricid and two erinaceids from the White River Oligocene. + Geol. Ser., Field Mus. Nat. Hist., 6:245-272, figs. 60-74. + +SCOTT, W. B. and JEPSEN, G. L. + 1936. The mammalian fauna of the White River Oligocene--Part I. + Insectivora and Carnivora. Trans. Amer. Philos. Soc., n. s., + 28:1-153, 22 pls., 7 figs. + +SIMPSON, G. G. + 1944. Tempo and mode in evolution. New York: Columbia Univ. Press, + xviii + 237 pp., 36 figs. + + 1953. The major features of evolution. New York: Columbia Univ. + Press, xx + 434 pp., 52 figs. + +_Transmitted June 24, 1963._ + + + + + +End of the Project Gutenberg EBook of Records of the Fossil Mammal +Sinclairella, Family Apatemyidae, From the Chadronian and Orellan, by William A. Clemens + +*** END OF THE PROJECT GUTENBERG EBOOK 30297 *** |