AMERICAN MUSEUM Norntates PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK, N.Y. 10024 Number 3130, 29 pp., 25 figures, 2 tables May 24, 1995 The Morphology and Relationships of Australochelys, an Early Jurassic Turtle from South Africa EUGENE S. GAFFNEY,1 AND JAMES W. KITCHING2 ABSTRACT Australochelys from the Early Jurassic Elliot (Cryptodira plus Pleurodira) than to Proganoche- Formation of South Africa is the oldest African lys. These characters include a sutured basipter- turtle. Known only from the skull and a shell frag- ygoid articulation and middle ear region partially ment, Australochelys has many primitive chelo- enclosed laterally. Australochelys is hypothesized nian characters in common with the Late Triassic as the sister taxon to the Casichelydia; together Proganochelys, such as a large interpterygoid va- they form the Rhaptochelydia. The relationships cuity and a lacrimal foramen. Australochelys has of Australochelys show that the beginning stages large orbits and a ventral basioccipital tubercle, of the unusual turtle hearing mechanism evolved characters that only occur in Proganochelys. How- before the origin ofthe modem turtle groups. Ak- ever, because Australochelys has a series of ad- inesis preceded or accompanied the enclosure of vanced characters in common with the Casiche- the hypertrophied middle ear region in the early lydia, it is more closely related to the Casichelydia evolution of the hearing mechanism. INTRODUCTION Australochelys, the oldest turtle from Af- described in a short paper (Gaffney and rica, reveals an important stage in the early Kitching, 1994) that did not include a de- history ofturtles. Australochelys was recently tailed morphological description or extended 1 Curator, Department of Vertebrate Paleontology, American Museum of Natural History. 2 Bernard Price Institute for Palaeontological Research, University ofthe Witwatersrand, Johannesburg 2001, South Africa. Copyright © American Museum of Natural History 1995 ISSN 0003-0082 / Price $3.30 2 AMERICAN MUSEUM NOVITATES NO. 3130 Fig. 1. Australochelys africanus Gaffney and Kitching, 1994, BP/1/4933. Dorsal view of skull. Ster- eophotograph. See fig. 3A for key. character discussion. The purpose ofthis pa- terpreted here, is that it is advanced over per is to provide more descriptive informa- Proganochelys but lacks derived characters tion and character discussions. of either Cryptodira or Pleurodira. In addi- The significance of Australochelys, as in- tion to Gaffney and Kitching (1994), relevant Fig. 2. Australochelys africanus Gaffney and Kitching, 1994, BP/1/4933. Ventral view of the skull. Stereophotograph. See fig. 3B for key. 1995 GAFFNEY AND KITCHING: MORPHOLOGY OF AUSTRALOCHELYS 3 B labial ridge apertura narium interna lingual ridge interpterygoid vacuity basipterygoid process Fig. 3. Australochelys africanus Gaffney and Kitching, 1994, BP/1/4933. A. Dorsal view of skull. B. Ventral view of skull. background papers are: Gaffney (1990) for AcKNowLEDGMENTs Proganochelys, Gaffney et al. (1987) for the We are most grateful to Mr. I. van Rooyen earliest cryptodire, Kayentachelys, and Gaff- of the farm Bormansdrift for his kindness, ney and Meylan (1988) for turtle phylogeny hospitality, and for permitting one ofus (J.K.) in general. The following skull description of access to his land to collect fossils. Dr. M. A. Australochelys assumes some familiarity with Raath helped with information on the Gokwe the skull of Proganochelys (Gaffney, 1990) Formation. Dr. B. S. Rubidge, director ofthe and general turtle skull morphology as pre- Bernard Price Institute, very graciously sented in Gaffney (1979). The descriptive opened the facilities and collections of that section here follows the order in Gaffney institution to one ofus (E.G.). The high qual- (1979). ity of the figures is due to the skills of F. Before the discovery ofAustralochelys, the Ippolito, E. Heck (fig. 25), and C. Tarka (fig. oldest known African turtle was the frag- 19). The senior author is particularly grateful mentary specimen identified by Nesbitt and to A. Schermerhorn for improving the manu- Bond (1972) as a turtle from the Gokwe For- script and assisting in its preparation. mation of Zimbabwe. At that time it was on the goodwill and questionably dated as Late Jurassic. More re- Everyone is dependent cently these and other turtle specimens from generosity of colleagues who willingly give the Gokwe Formation of Zimbabwe have their time in reviewing papers. We are par- been reinterpreted as being more likely Late ticularly fortunate to have benefited from the Cretaceous in age (M. Raath, personal com- efforts offour ofour associates: D. Brinkman, mun. to J. Kitching, August 1993). At pres- P. Meylan, R. Reisz, and 0. Rieppel, who ent, the next oldest known African turtles are have generously helped improve this paper. the Early Cretaceous pleurodires summa- rized in de Broin (1989). This represents a gap of some 60 million years, between Aus- ABBREVILATIONS tralochelys and the Early Cretaceous pleu- BP Bernard Price Institute, Johannes- rodires. burg, South Africa 4 AMERICAN MUSEUM NOVITATES NO. 3130 MB Museum fur Naturkunde, Berlin, is defined to consist of Australochelys plus Germany Casichelydia. SMNS Staatliches Museum fur Naturkunde, Stuttgart, Germany FAMILY AUSTRALOCHELYIDAE Gaffhey and Kitching, 1994 bo basioccipital bs basisphenoid Australochelys Gaffney and Kitching, 1994 ex exoccipital fr frontal TYPE SPECIES: Australochelys africanus ju jugal Gaffhey and Kitching, 1994. mx maxilla KNowN DISRmurIoBN: Early Jurassic, one na nasal locality in Orange Free State, South Africa. op opisthotic ETYMOLOGY: australos, Greek for "south"; pa parietal chelys, Greek for "turtle." pal palatine DIAGNOsIs: As for species. pf prefrontal pm premaxilla Australochelys africanus po postorbital Gaffhey and Kitching, 1994 pr prootic TYPE SPECiMEN: Bernard Price Institute, pt pterygoid University of the Witwatersrand, Johannes- qj quadratojugal burg, South Africa, BP/l/4933; consists of a qu quadrate skull without lowerjaws and a fragment from so supraoccipital the bridge area of the shell. sq squamosal LocALITr: Bormansdrift (133), Clocolan vo vomer District, Orange Free State, South Africa. Map sheet: 1:50,000 2827 CD Mekoatlengsnek 28057'33"S, 27026'05"E (Kitching and Raath, SYSTEMATICS 1984). ORDER TESTUDINES HORIZON: Tritylodon Acme-Zone, (mid- dle) Elliott Formation, Early Jurassic (Olsen DLAGNosIs: As in Gaffney and Meylan and Galton, 1984). (1988). COLLECTOR: James W. Kitching, March 1980. Rhaptochelydia Gaffney and Kitching, 1994 ETYMOLOGY: africanus, from Africa. ETYMOLOGY: rhaptos (not "rhaptors" Gaff- ney and Kitching, 1994, in error), Greek for "sewn" in allusion to the sutured basiptery- DIAGNOSIS goid articulation; chelys, Greek for "turtle." Kitching, 1994) EMENDED DiAGNosIs: Posterior margin of (modified from Gaffney and temporal roof extends over opisthotic; pal- Characters unique to Australochelys among atal teeth few or absent; basipterygoid artic- turtles: Orbit larger in relative size than in ulation closed (sutured); cranioquadrate space any other turtle; lacrimal foramen at least a well-defined foramen or canal, the canalis three times larger than in Proganochelys; ex- cavernosus, not an open space; stapes prob- ternal nares elongate in contrast to all turtles; ably articulating with a tympanic membrane, vomers arched dorsally, narrow posteriorly, not with the quadrate; ventral ridge on op- and very broad anteriorly in a unique con- isthotic; distal end of opisthotic covered lat- figuration. erally by squamosal and/or quadrate; par- Primitive chelonian characters found only occipital process ofopisthotic tightly sutured in Proganochelys and Australochelys within to braincase; crista supraoccipitalis a distinct turtles but also found in primitive tetrapods: vertical sheet of bone. Divided external nares formed by premax- DIsCussIoN: This taxon, Rhaptochelydia, illae; large interpterygoid vacuity as in Pro- 1995 GAFFNEY AND KITCHING: MORPHOLOGY OF A USTRALOCHELYS 5 ganochelys; unenclosed middle ear region; a DERMAL ROOFING ELEMENTS recessed, funnel-shaped, cavum tympani ab- (figs. 1, 3-6) sent; lacrimal foramen present; recessus sca- lae tympani and fenestra perilymphatica ab- The nasal area of Australochelys is char- sent; foramen jugulare posterius with at least acterized by a deep snout, large fossa nasalis, a medial edge absent; cultriform process pres- and an elongate apertura narium externa. In ent. contrast, Proganochelys has a relatively small Advanced chelonian characters found only snout, small fossa nasalis, and a less elongate in Australochelys and Casichelydia (Cryp- apertura narium externa. These features in todires plus Pleurodires): Basipterygoid artic- Australochelys are probably autapomorphic, ulation sutured; stapes probably does not ar- although a large fossa nasalis is common in ticulate directly with quadrate but may have other amniotes and does occur in some Cas- attached to a tympanic membrane supported ichelydia. Australochelys has a paired aper- by the acute posterior edge of the quadrate; tura narium externa, with a well-developed distal end ofopisthotic covered by quadrate; internarial bar, as in Proganochelys. The in- canalis cavernosus a well-defined canal; few ternarial bar is broad dorsally, becomes nar- or no palatal teeth; crista supraoccipitalis a rower ventrally, but its ventral limits are not distinct vertical sheet ofbone; temporal roof preserved. The dorsal end