A new galesaurid (Therapsida: Cynodontia) from the Lower Triassic of South Africa

A new galesaurid cynodont, Progalesaurus lootsbergensis gen. et sp. nov., is described on the basis of a well‐preserved skull, lower jaw, right scapula and left atlantal neural arch. Autapomorphies of Progalesaurus include postcanine teeth bearing numerous mesial and distal accessory cusps that flank a recurved main cusp, a post‐temporal fenestra bordered by the squamosal ventrally and a large external naris. Progalesaurus is similar to Galesaurus in possessing a poorly defined masseteric fossa on the dentary, a strongly recurved main cusp of the postcanine dentition, an incomplete secondary palate and a similar basisphenoid‐parasphenoid morphology. A cladistic analysis of ten early cynodont genera resolves a monophyletic Galesauridae encompassing Cynosaurus, Progalesaurus and Galesaurus, although support for this clade is weak. Procynosuchus and Dvinia are placed at the base of Cynodontia whereas Thrinaxodon and Platycraniellus are positioned higher, but outside of Eucynodontia. The holotype and only known specimen of Progalesaurus was collected during systematic prospecting of Permo/Triassic boundary strata at New Lootsberg Pass, Graaff‐Reinet District, South Africa. The discovery of Progalesaurus increases the number of valid Early Triassic cynodonts to four and sheds light on the tempo of early cynodont diversification after the end‐Permian mass extinction.

[1]  R. Reisz,et al.  Owenetta kitchingorum, sp. nov., a small parareptile (Procolophonia: Owenettidae) from the Lower Triassic of South Africa , 2002 .

[2]  C. Koeberl,et al.  Catastrophic events and mass extinctions : impacts and beyond , 2002 .

[3]  Smith,et al.  Altered river morphology in south africa related to the permian-triassic extinction , 2000, Science.

[4]  W. J. Hillenius.  Septomaxilla of nonmammalian synapsids: Soft‐tissue correlates and a new functional interpretation , 2000, Journal of morphology.

[5]  G. King,et al.  The dicynodont Lystrosaurus from the Upper Permian of Zambia: evolutionary and stratigraphical implications , 1997 .

[6]  Roger M. H. Smith.  Changing fluvial environments across the Permian-Triassic boundary in the Karoo Basin, South Africa and possible causes of tetrapod extinctions , 1995 .

[7]  J. Wible,et al.  Homologies of the Prootic Canal in Mammals and Non-mammalian Cynodonts , 1995 .

[8]  T. Worsley.  The great paleozoic crisis: life and death in the permian. P.H. Erwin, 1993. Columbia Univ. Press, New York, Paperback, xi + 327 pp. ISBN 0-231-07467-0 , 1994 .

[9]  J. Hopson.  Synapsid Evolution and the Radiation of Non-Eutherian Mammals , 1994 .

[10]  G. Rougier,et al.  Reconstruction of the cranial vessels in the Early Cretaceous mammal Vincelestes neuquenianus: implications for the evolution of the mammalian cranial vascular system , 1992 .

[11]  J. Wible,et al.  The septomaxilla of fossil and recent synapsids and the problem of the septomaxilla of monotremes and armadillos , 1990 .

[12]  S. Fourie.  THE CRANIAL MORPHOLOGY OF THRINAXODON-LIORHINUS , 1974 .

[13]  T. Kemp.  Whaitsiid Therocephalia and the origin of cynodonts , 1972 .

[14]  L. Tatarinov.  Morphology and systematics of the northern Dvina Cynodonts lReptiliac Therapsidas upper Permianr , 1968 .

[15]  A. Brink.  On two new specimens of Lystrosaurus-zone cynodonts , 1965 .

[16]  R. L. Konizeski.  PALEOECOLOGY OF THE MIDDLE PLIOCENE DEER LODGE LOCAL FAUNA, WESTERN MONTANA , 1957 .

[17]  H. Rigney.  The morphology of the skull of a young Galesaurus planiceps and related forms , 1938 .

[18]  F. R. Parrington.  On the Tooth-Replacement in Theriodont Reptiles , 1936 .

[19]  R. Lydekker.  Catalogue of the Fossil Reptilia and Amphibia in the British Museum (Natural History) , 1890, Nature.