Craniofacial Morphology of Vintana Sertichi (Mammalia, Gondwanatheria) from the Late Cretaceous of Madagascar

ABSTRACT

The Gondwanatheria are an enigmatic clade of Cretaceous and Paleogene mammals known from South America, Africa, Madagascar, India, and the Antarctic Peninsula. The eight valid species—each belonging to a monotypic genus and the first of which was described only 30 years ago—are represented almost exclusively by isolated teeth, in addition to fragmentary dentaries attributed to Sudamerica, Gondwanatherium, Ferugliotherium, and an unnamed taxon from Tanzania. No cranial (skull exclusive of lower jaw) or postcranial material has heretofore been assigned to the Gondwanatheria, a severe limitation that has precluded a comprehensive assessment of phylogenetic affinities. Here we describe, in detail, the first cranial specimen of a gondwanatherian mammal. This material consists of a complete and well-preserved cranium of the sudamericid Vintana sertichi, recovered from the Upper Cretaceous (Maastrichtian) Maevarano Formation in the Mahajanga Basin of northwestern Madagascar. Salient features of the cranium include elongate, scimitar-like jugal flanges, huge orbits, strong klinorhynchy, and a vaulted nuchal region. Micro-computed tomography greatly facilitated the delineation of sutures and the description of internal morphology. The cranial features of Vintana are compared with those of a broad range of synapsids, with particular concentration on other Mesozoic mammaliaforms. The cranium of Vintana exhibits a mosaic of extremely primitive and extremely derived features. It is the second largest known for a Mesozoic mammaliaform, superseded only by that of the eutriconodontan Repenomamus giganticus from the Early Cretaceous of China. Vintana is the largest known Late Cretaceous mammaliaform; it is also the largest known Mesozoic mammaliaform from Gondwana.

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ACKNOWLEDGMENTS

We thank J. Thostenson and M. Hill (American Museum of Natural History Microscopy and Imaging Facility, New York) and J. Diehm and B. Ruether (Avonix Imaging, Plymouth, Minnesolta) for μCT scanning of UA 9972; Phoenix Analysis & Design Technologies (Tempe, Arizona) for providing a high-quality 3D print of the cranium; D. Boyer (Duke University) for μCT scanning comparative material of Thrinaxodon; J. Neville (Stony Brook University [SBU]) for taking the photographs in Figs. 1, 3–6; E. Ambika and T. Salerno (SBU) and Kenneth Wheeler (Ohio University) for assistance with μCT imaging; L. Betti-Nash (SBU) for skillfully executing various drawings, for assistance in arranging and labeling the figures, and for incredible patience, not to mention grace under pressure; F. Grine for providing access to comparative material of Thrinaxodon; A. Pritchard for assistance with references; and D. Boyer (Duke University), E. Dumont (University of Massachusetts–Amherst), B. Demes (SBU), M. Geiger (University of Zürich), W. Hillenius (College of Charleston), C. Kammerer (Museum für Naturkunde, Berlin), Z.-X. Luo (University of Chicago), G. Rougier (University of Louisville), I. Ruf (Universität Bonn), M. Sánchez-Villagra (University of Zürich), and T. Smith (Slippery Rock University) for discussion; and Z.-X. Luo for taking on the task of reviewing this large manuscript and for providing many insightful comments. This research was supported by grants from the National Geographic Society (8597-09) and the National Science Foundation (BCS-0610514, EAR-0446488, EAR-1123642).

Handling editor: Jeffrey A. Wilson