New mammal faunal data from Cerdas, Bolivia, a middle-latitude Neotropical site that chronicles the end of the Middle Miocene Climatic Optimum in South America

ABSTRACT

We provide new and revised identifications of mammals from the early middle Miocene (Langhian age, Colloncuran South American Land Mammal Age [SALMA]) of Cerdas, Bolivia. We also formally name a new typothere notoungulate, Hegetotherium cerdasensis, sp. nov., that can be distinguished by the absence of an external talonid sulcus on m3 and its small size (15–25% smaller than Hegetotherium mirabile). We refer several typothere specimens from Nazareno, Bolivia, to H. cerdasensis, which suggests that the two sites are of similar age. We report the first sparassodont and astrapothere remains from Cerdas. Sparassodont remains include an associated basicranium and mostly complete mandible; the species appears to represent a new, small-bodied borhyaenoid. Astrapothere remains consist of many tooth fragments from a new species of the subfamily Uruguaytheriinae. A partial sloth dentary from Cerdas likely pertains to the subfamily Megatheriinae and is the first report of the family Megatheriidae from the site. A newly discovered peltephilid armadillo specimen includes a partial articulated carapace that supports recognition of the Cerdas taxon as a new species. The two dasypodids of Cerdas (one Euphractini, one Eutatini) represent two new species closely related to undescribed species from the late middle Miocene (Serravallian age, Laventan SALMA) of Quebrada Honda, Bolivia. The mammals of Cerdas indicate that (1) the middle latitudes (southern tropics) contributed significantly to the diversity of Miocene mammal communities in South America; and (2) the Middle Miocene Climatic Optimum was a key factor in the differentiation of South American mammal assemblages.

Citation for this article: Croft, D. A., A. A. Carlini, M. R. Ciancio, D. Brandoni, N. E. Drew, R. K. Engelman, and F. Anaya. 2016. New mammal faunal data from Cerdas, Bolivia, a middle-latitude Neotropical site that chronicles the end of the Middle Miocene Climatic Optimum in South America. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2016.1163574.

ACKNOWLEDGMENTS

We thank G. Billet, E. Cerdeño, and A. Kramarz for helpful discussions and information related to the manuscript; P. Holroyd (UCMP), A. Kramarz (MACN), D. Miao (KU), M. Reguero (MLP), and W. Simpson (FMNH) for facilitating access to specimens in their care; J. Carrillo and A. Kramarz for providing constructive criticism that improved the manuscript; D. Auerbach, A. Catena, R. Chavez, J. Conrad, A. Deino, C. Garzione, L. Gibert, D. Hembree, P. Higgins, B. MacFadden, B. Saylor, J. Smith, and A. Zurita for assistance in the field; and M. Sánchez-Villagra for facilitating the publication of this paper by serving as Editor. This research was supported by the National Science Foundation (EAR 0819817 to D.A.C.), the National Geographic Society Committee for Research and Exploration (NGS 8115-06 to D.A.C.), the Fondo para la Investigación Científica y Tecnológica (PICTO2012/104 to A.A.C.), and the Universidad Nacional de La Plata (N-724 to A.A.C.).