First skull and associated postcranial bones of Macraucheniidae (Mammalia, Litopterna) from the Deseadan SALMA (late Oligocene) of Cabeza Blanca (Chubut, Argentina)

ABSTRACT

The first skull associated with postcranial elements of Macraucheniidae (Litopterna) from the Sarmiento Formation in Cabeza Blanca (Chubut, Argentina) are described herein. The material consists of a nearly complete skull, nearly complete right humerus, left metacarpal IV, and three phalanges (proximal, intermediate, and distal of the same digit) of the same individual. It is compared with the Santacrucian genus Theosodon Ameghino, the Colhuehuapian Cramauchenia Ameghino, and the Deseadan species Coniopternium andinum and C. primitivum Soria and Hoffstetter. The comparative study leads us to recognize this specimen as Cramauchenia normalis. The presence of this species in Cabeza Blanca increases its biochronological distribution to Deseadan South American Land Mammal Age (SALMA) (late Oligocene).

ACKNOWLEDGMENTS

We thank M. Bond for his valuable contribution in the first stage of the work, E. Cerdeño for the critical reading of the manuscript and her suggestions, L. Reiner (MPEF) for the preparation of the fossil material, R. Taylor (CENPAT) and R. Vacca (MPEF) for their technical support during the fieldtrip, G. Massaferro (CENPAT) for help with the English version, J. Briguglio (CENPAT) and M. Marín (CENPAT) for help with the figures, and A. Kramarz (MACN) and K. Wellspring (ACM) for the access to collections under their care. We also express our gratitude to A. Venter and family (“Estancia El Molino” owners) for their hospitality during the field work. Finally we thank J. Gelfo, an anonymous reviewer, and editor D. Croft who provided careful reviews that improved the manuscript. This study was supported by CONICET PIP 2628 and PICT-SECYT 07/32344.