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New Jurassic Mammials from Non-Tribosphenic Theria

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New Jurassic Mammials from Non-Tribosphenic Theria NEW JURASSIC MAMMIALS FROM COMO BLUFF, WYOMING, AND THE INTERRELATIONSHIPS OF NON-TRIBOSPHENIC THERIA DONALD R. PROTHERO BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY VOLUME 167: ARTICLE 5 NEW YORK: 1981 7~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 34 v,~~~~~~~~~~~~~~~~~ "AT~~~ ~ ~ ~ 4K~~~~~~~~~~~~~~~4 4 ' j4'~~"T'4"444 4 ~~~~Z '4'''44444444~ 44~ *4~~4.4.4"~ " '- -,44~'4~':J"'-.'4 '~ " '" 4 4'', 4 ;q~W'7'44f~~~44~~~~~~~~444.4''"4~ ~ ~ '4'4"'~~~~~~~~~~~~~~' '4 '~~~~~~~~~~4''4,'7 ~ 4 ~ '.4 '4 4444.~ .444?,k4~4.4~X'4 '4~~~~/4:~~~~~.~~~'44444444.,~~~~~~~~~~ ~~ ~ ~ ~ ~~ 4"'' "'4 4" .~~~~~~~~~~~~~.. 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PROTHERO Graduate Student, Department of Geological Sciences Columbia University BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY VOLUME 167: ARTICLE 5 NEW YORK: 1981 BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY Volume 167, article 5, pages 277-326, figures 1-12, tables 1-9 Issued February 26, 1981 Price: $3.20 a copy ISSN 0003-0090 Copyright ©) American Museum of Natural History 1981 CONTENTS Abstract ........................ 281 Introduction .............................. 281 Abbreviations ........................ 282 Acknowledgments ........................ 282 Stratigraphy and Localities ........................ 283 Systematic Descriptions ........................ 286 Taxa Known from Upper Jaws ........................ 286 Comotherium, New Genus .............................. 286 Melanodon and Herpetairus ......................... 289 Melanodon Simpson, 1927 ........................ 290 Herpetairus Simpson, 1927 ........................ 292 Taxa Known from Lower Jaws ........................ 293 Amblotherium Owen, 1871 .............................. 293 Dryolestes Marsh, 1878 .............................. 293 Laolestes Simpson, 1927 ........................ 295 Kepolestes Simpson, 1927 ........................ 297 Discussion ........................ 297 General Tooth Characters ........................ 299 Lower Jaw Characters ........................ 301 Lower Tooth Characters ........................ 305 Upper Tooth Characters ........................ 309 Cladogram Discussion ........................ 312 Symmetrodont Monophyly ........................ 313 Position of Amphidontids ........................ 317 Position of Amphitherium ........................ 319 Classification ........................ 320 Literature Cited ........................ 323 ABSTRACT A joint American Museum of Natural History- trary to the condition reported in Kimmeridgian Yale University expedition reopened Quarry Nine Portuguese dryolestids. at Como Bluff, Wyoming, in 1968-1970. This lo- The systematics of primitive Theria are re- cality had produced all but six of about 250 Ju- viewed, and an hypothesis of relationships for the rassic mammal specimens known from North non-tribosphenic Theria is proposed. This hy- America prior to 1968. During the renewed col- pothesis corroborates the hypothesis of McKenna lecting, four additional prospects were found in (1975). It is concluded that the symmetrodonts are the vicinity, and 25 fossil mammal jaws and nu- a monophyletic group, and that Amphitherium is merous teeth were collected. most closely related to the dryolestoids. A cladis- A new genus and species of dryolestid, Com- tic classification of the non-tribosphenic Theria is otherium richi, is described. The dryolestid gen- proposed. Six new taxa are named: sublegions era Melanodon and Herpetairus are reviewed and Amphidontoidea and Spalacotherioidea, and in- rediagnosed. The anterior dentition of Melanodon fraclasses Tinodontida, Spalacotheriida, Am- goodrichi and better material of Herpetairus hu- phitheriida, and Dryolestida. It is strongly urged milis are described. The crown and labial views that the term "pantothere" be abandoned, be- of Kepolestes, previously obscured in matrix, are cause it has misleading phylogenetic connotations described. No dryolestid jaw in this collection and because it obscures non-tribosphenic therian shows any trace of a coronoid or splenial, con- diversity. INTRODUCTION The history of the Mammalia during the sponsored an expedition that reopened Quar- Jurassic Period has always been one of the ry Nine in the summers of 1968 to 1970. This most interesting, yet poorly documented expedition was led by Thomas H. Rich (then phases of mammalian evolution. Mammals of the American Museum) and Charles R. first appeared in the Rhaeto-Lias (late Trias- Schaff (then of Yale University). The result sic-early Jurassic, about 190 Ma), but are of this expedition was a large collection of known from only three medial Jurassic lo- fragmentary vertebrates and invertebrates, calities and four late Jurassic localities. With including 25 mammal jaws and numerous the exception of one skeleton (Henkel and teeth. This collection has been expertly pre- Krebs, 1977), no Jurassic therian mammal is pared and given preliminary identification by known from more than fragmentary teeth Mr. Schaff, but has remained undescribed and jaws. until I took up the task at the suggestion of In North America, Jurassic mammals are Dr. Malcolm C. McKenna. Dr. Eugene S. recorded only from the Morrison Formation, Gaffney has described the turtles in the col- which is Tithonian (latest Jurassic), about lection (Gaffney, 1979). Dr. A. W. Crompton 145 Ma. All but six of more than 250 mammal discusses aspects of dental occlusion else- specimens collected prior to 1968 have come where. In the present paper I discuss the from Quarry Nine at Como Bluff, Wyoming. therian mammals in the new collection, in- In the late 1870s and 1880s, the crews of Oth- cluding a new genus and species of dryoles- niel C. Marsh discovered these specimens in tid. Quarry Nine. They were redescribed by While my study of the new form described Simpson (1927, 1929). Except for the pau- herein was in progress, it became necessary rodont Araeodon (Simpson, 1937), no North to review the systematics of the rest of the American Jurassic mammals have been re- dryolestoids. New developments in phylo- ported or described since 1929. genetic analysis, known as "cladistics" or For this reason, at the suggestion of Mal- "phylogenetic systematics" (Hennig, 1965, colm C. McKenna,- the American Museum 1966) are employed for reasons discussed of Natural History and Yale University below. The interrelationships of the numer- 281 282 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY VOL. 167 ous taxa of "pantotheres" have been ne- terial will serve as an immediate test of this glected since Simpson's monographs (1928, hypothesis. I hope that this preliminary hy- 1929). Simpson himself never attempted to pothesis of relationships stimulates other analyze the relationships of the individual workers to attempt to falsify it and to pro- taxa. A cladistic framework not only makes duce a more parsimonious explanation of the this possible but demands it. distribution of characters. In the analysis of primitive versus derived character states and morphocline polarities ABBREVIATIONS in dryolestoids, the analysis naturally ex- panded into all the primitive Theria and the- AMNH, Department of Vertebrate Paleon- rian sister groups. The cladogram (a branch- tology, American Museum of Natural His- ing diagram of relationships using only tory. shared derived character states) was arbi- USNM, Division of Vertebrate Paleontolo- trarily restricted to the non-tribosphenic gy, National Museum of Natural History, Theria. Eventually it will be possible to in- Smithsonian Institution clude the rest of the Mammalia in a much YPM, Peabody Museum of Natural History, larger cladogram currently in progress Yale University (McKenna, 1975). Kimmeridgian (late Jurassic) dryolestoids ACKNOWLEDGMENTS from Guimarota, Portugal, have recently Special thanks are due to three people who been described (Kiihne, 1961, 1968; Krebs, made the project possible. Dr. Thomas H. 1969, 1971; Henkel and Krebs, 1977). How- Rich initiated the project as the potential ever, none of the taxa except Crusafontia, subject for a Ph.D. thesis. He spent many from the Lower Cretaceous of Unia, Spain months in the field and laboratory working (Henkel and Krebs, 1969), has been diag- on it, but did not see it to its completion. Mr. nosed or figured adequately in the literature, Charles R. Schaff put in many months in the and so could not be incorporated into this field and with his customary expertise pre- study. A number of tantalizing figures of pared the specimens. Dr. Malcolm C. named, but still undescribed forms appeared McKenna first suggested the project to both in a paper by Kuhne (1968), but without de- Dr. Rich and to me, and has guided the pres- scriptions or diagnoses.' I have examined all ent manuscript through several revisions. the North American material, and have stud- The field crew at Como Bluff was large ied excellent sterophotographs of the British and changed from year to year, but included material, courtesy of Dr. A. W. Crompton. (in alphabetical order): B. Abel, M. Albert,
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