Novitatesamerican MUSEUM PUBLISHED by the AMERICAN MUSEUM of NATURAL HISTORY CENTRAL PARK WEST at 79TH STREET NEW YORK, N.Y
Total Page：16
File Type：pdf, Size：1020Kb
NovitatesAMERICAN MUSEUM PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET NEW YORK, N.Y. 10024 U.S.A. NUMBER 2552 OCTOBER 15, 1974 EDWIN H. COLBERT AND JOHN W COSGRIFF Labyrinthodont Amphibians from Antarctica Labyrinthodont Amphibians from Antarctica EDWIN H. COLBERT Curator Emeritus, The Amer'wan Museum of Natural History Professor Emeritus, Columbia University Curator of Vertebrate Paleontology The Museum of Northern Arizona, Flagstaff JOHN W COSGRIFF Associate Professor of Biology Wayne State University, Michigan AMERICAN MUSEUM NOVITATES NUMBER 2552, pp. 1-30, figs. 1-20, table 1 ISSN 0003-0082 Issued October 15, 1974 Price $1.95 Copyright © The American Museum of Natural History 1974 ABSTRACT ian which, following further comparative studies, Labyrinthodont amphibians from the Lower is identified in the present paper as a brachyopid. Triassic Fremouw Formation of Antarctica are The discovery of this specimen-an accidental described. These consist of a fragment of a lower event tangential to Barrett's study of the geology jaw collected at Graphite Peak in the Transant- of the Transantarctic Mountains in the general arctic Mountains in December, 1967, and various region of the Beardmore Glacier-was the stimu- fossils from Coalsack Bluff (west of the lus for a program of vertebrate paleontological Beardmore Glacier and some 140 km., or about collecting in Antarctica. An expedition under the 88 miles, northwest of Graphite Peak) during the auspices of the Institute of Polar Studies of The austral summer of 1969-1970 and from near the Ohio State University and the National Science junction of the McGregor and Shackleton Gla- Foundation went to the Beardmore Glacier area ciers (about 100 km., or 60 miles, more or less, during the austral summer of 1969-1970 for the to the east and a little south of Graphite Peak) during the austral summer of 1970-1971. Two express purpose of searching for and collecting new genera and species are described. Austro- fossil tetrapods of Triassic age. Fossils were brachyops jenseni is a brachyopid showing resem- collected at Coalsack Bluff, about 35 miles east blances to Batrachosuchus from the Lower Trias- of the Beardmore Glacier during this field season. sic of South Africa and to Hadrokkosaurus from A second expedition during the austral summer the Middle Triassic of North America. Cryobatra- of 1970-1971 collected fosslls near the conflu- chus kitchingi is a lydekkerinid related to Lydek- ence of McGregor and Shackleton glaciers, some kerina and Limnoiketes from the Lower Triassic 90 miles or so west of the Beardmore Glacier, of South Africa. In addition an isolated tabular and about 60 miles west of the original discovery bone from Bluff represents a temno- Coalsack site at were collected spondyl amphibian of possible capitosaurid or Graphite Peak. Amphibians benthosuchid relationships. These fossils supple- at both localities. ment the evidence of reptiles collected from the The purpose of the present paper is to give Fremouw Formation, to indicate a probable liga- preliminary lists and descriptions of the fossil tion between Antarctica and South Africa and amphibians collected in Antarctica up to now. paleozoogeographic relationships between Ant- The first season of field work at Coalsack arctica and other parts of Gondwanaland and Bluff was carried on by the senior author with even of Laurasia. William Breed of the Museum of Northern Ari- zona, Flagstaff; James A. Jensen of Brigham INTRODUCTION Young University, Provo, Utah; and Jon S. Pow- The first fossil of a Triassic tetrapod found in ell of the University of Arizona, Tucson. The sec- Antarctica was discovered December 28, 1967, ond season of field work at McGregor and Shack- by Dr. Peter J. Barrett, then of the Institute of leton glaciers was done by James W. Kitching of Polar Studies, The Ohio State University, Colum- the Bernard Price Institute of Palaeontology, bus, now of Victoria University, Wellington, New University of the Witwatersrand, Johannesburg, Zealand. The specimen, consisting of a fragment Union of South Africa; with John Ruben of the from a left mandibular ramus of a labyrinth- University of California, Berkeley; and briefly odont amphibian, was collected in the Fremouw Thomas Rich, then of Columbia University, New Formation, of early Triassic age, as exposed on York. Both paleontological parties were sections the slopes of Graphite Peak in the Transantarctic of larger geological study units all under the lead- Mountains, about 400 miles from the South Pole. ership of David H. Elliot of the Institute of Polar The specimen was submitted to the senior Studies of The Ohio State University, Columbus. author for identification, and it has been The work was done under the auspices of the described and figured in previous papers (Barrett, National Science Foundation of the United Baillie, and Colbert, 1968; Colbert, 1971c). It States of America. represents a rather large labyrinthodont amphib- The fossils described herein were prepared by 3 .4 AMERICAN MUSEUM OF NATURAL HISTORY Mr. David Lawler and Miss Camas Lott. The McGregor-Shackleton Glacier region have been drawings (figs. 1-11, 13) were made by Miss outlined in previous contributions on Antarctic Pamela Lunge of the Museum of Northern Ari- Triassic fossils (Elliot, Collinson, and Powell, zona and Mr. William E. Loechel of the School of 1972, pp. 387-392; Colbert, 1974, pp. 5-12). Suf- Medicine, Wayne State University. The photo- fice it to say that the Fremouw beds, the lowest graphs were made by Mr. Marc Gaede of the Mu- of the Mesozoic units in the Transantarctic Moun- seum of Northern Arizona. The work was sup- tains, are composed of sandstones, shales, and silt- ported in part by a grant from the National Sci- stones of varying consistency and composition as ence Foundation, no. GV-2543 1. is characteristic of freshwater continental deposits. The sediments at Coalsack Bluff and at Mc- Abbreviations for Illustrations Gregor-Shackleton glaciers are cyclic, consisting Ang, angular of coarse, almost conglomeratic channel deposits c, corpus of the pterygoid at the base (Coalsack Bluff fossil beds) and fine cr. bpt, basipterygoid crest floodplain deposits at the top (Mount Kenyon cr. spt, suprapterygoid crest fossil beds), with intergradations between. The ept, platform for the epipterygoid; broken base bedding-plane exposures of fine-grained sediments of the epipterygoid at McGregor and Shackleton glaciers account for F, frontal the prevalence of skeletons or partial skeletons f.st, stapedial fossa at this locality, as contrasted with the isolated fa. a, articular facet bones found at Coalsack Bluff.' fo.ra., retroarticular fossa Thus we see the indications of two different Ip, interparietal J, jugal habitats, at Coalsack Bluff and Shackleton Gla- L, lacrimal cier, and these differences bear on the nature of Mx, maxilla the fossils. So far as the fossils are concerned, N, nasal the differences as mentioned above are those P, parietal between isolated bones and articulated speci- p. b, posterior border of the pterygoid corpus mens-the former easily freed from the some- p. ra, retroarticular process what coarse and friable sands containing them, p.b. eo, basal process of the exoccipital, sutural the latter firmly enclosed in their matrices. surface on the pterygoid for the basal process of the exoccipital DESCRIPTIONS OF FOSSILS Pa, prearticular Pin, pineal Pmx, premaxilla CLASS AMPHIBIA Po, postorbital SUBCLASS LABYRINTHODONTIA Pof, postfrontal Prf, prefrontal ORDER TEMNOSPONDYLI quadratojugal Qj, SUPERFAMILY BRACHYOPOIDEA r. as, ascending ramus of the pterygoid r. c, conical recess FAMILY BRACHYOPIDAE r. pl, palatal ramus of the pterygoid r. qu, quadrate ramus of the pterygoid Brachyopids form a distinctive group of the s.a. ca, sulcus for the intemal carotid artery Temnospondyli, highly specialized in certain fea- Sa, surangular tures of cranial anatomy. Genera included in the Smx, septomaxilla ' We are indebted to Professor James W. Collinson Sq, squamosal of The Ohio State University, for clarification of the St, supratemporal sedimentary characters of the Fremouw Formation, T, tabular as based on his studies in Antarctica. This corrects the discussion in Colbert (1974, pp. 2 and 11), in which STRATIGRAPHIC RELATIONSHIPS it was implied that the differences in the fossils col- lected at the two Antarctic localities was due to local The stratigraphic relationships of the Fre- sedimentary differences rather than stratigraphic dis- mouw Formation at Coalsack Bluff and in the tinctions. COLBERT AND COSGRIFF: AMPHIBIANS 5 family range from the Late Permian into and Two recent additions to the family from the probably through the Middle Triassic and encom- Lower Triassic of Australia are: Brachyops allos pass an exceptionally large geographic range. Howie, 1971, from the Rewan Series of Queens- With the addition of the new material from Ant- land; and Blinasaurus townrowi Cosgriff(In press) arctica described below the family is now known from the Knocklofty Formation of Tasmania. from fossil assemblages on every continent, ex- The former species is based on a single skull and cept South America. It has been extensively the latter on a fairly extensive hypodigm of skull, described, reviewed, and revised three times in lower jaw, and postcranial material. recent years-by Watson (1956), Welles and Estes The new material from the Fremouw Forma- (1969), and Cosgriff (1969). These authors all tion that can be allocated to the Brachyopidae discuss the contents of the family, its diagnostic withl certainty includes the original jaw fragment morphologic characters, evolutionary relation- (AMNH' 9301) from Graphite Peak and an iso- ships among the various genera and species, and lated pterygoid bone (AMNH 9346) from Coal- stratigraphic and geographic occurrences. sack Bluff. The latter specimen is the more ade- quate for comparative purposes; it is distinct Contents of the Family enough in several of its features to be nominated The taxonomic history of the Brachyopidae the holotype of a new genus and species.