New remains of Cephalomys arcidens (Rodentia, Caviomorpha) and a redefinition of the enigmatic Cephalomyidae

Abstract

Cephalomys is the best-known cephalomyid, recorded in five localities in Argentina and known from well-preserved mandibles, fragments of skull, and a large number of isolated teeth, from both juveniles and adults. Despite this, a modern description is lacking and the validity of some species of Cephalomys has been questioned in the last few years. New material from the Deseadan locality of Cabeza Blanca (Chubut, Argentina), including skull fragments unknown for the species thus far, and well-preserved juvenile teeth, along with a large number of specimens from collections in Argentina, allow us to propose a more complete description of the genus and a new taxonomic arrangement for the Cephalomys species. We also analysed some dubious records of Cephalomys from Quebrada Honda and Pico Truncado and confirm that they are not part of this genus. We consider C. plexus to be a synonym of C. arcidens, we consider the combination previously proposed for C. bolivianus (as a species of Asteromys) to be valid, and we consider C. ceciae also to be a valid species. We performed a phylogenetic analysis including for the first time all cephalomyids (Cephalomys, Litodontomys, Cephalomyopsis, Soriamys and Banderomys) and possibly related genera (Perimys, Scotamys, Asteromys) to test the position of the family Cephalomyidae among the other caviomorph rodents, as well as its validity and internal relationships. The results recovered Cephalomyidae as a clade, including Cephalomys, Cephalomyopsis and Litodontomys. The monophyly of Cephalomys could not be confirmed. Soriamys and Banderomys were recovered within Cavioidea. Perimys, Scotamys and Asteromys were recovered within Chinchilloidea, and we analysed the implications of their positions within the group. The implications in terms of the biochron, distribution and evolutionary history of the Cephalomyidae, considering the new definition for the family proposed herein (including only Cephalomys, Cephalomyopsis and Litodontomys), are discussed, as well as inferences regarding caviomorph evolution at the scale of the entire group.

Keywords:

• Cavioidea
• Chinchilloidea
• Cephalomys
• Cephalomyidae
• Deseadan
• Patagonia

Acknowledgements

The present contribution is part of the lead author’s (FB) PhD thesis. FB thanks his thesis advisors (MTD and IMS) for providing materials and for all the valuable suggestions made, and advice given, during the PhD. For allowing access to specimens under their care, we thank Alejandro Kramarz and Stella Maris Álvarez (MACN, palaeovertebrate collection), Marcelo Reguero (MLP), Eduardo Rui Gómez and María Encarnación Pérez (MEF), Alberto Garrido and Belén Boilini (Museo Olsacher), Rodolfo Coria (Plaza Huincul), Pablo Teta and Sergio Lucero (MACN, mammals collection). Kate Wellspring (ACM), Christine Argot (MNHM) and Pati Pérez (MEF) provided photographs of specimens from USA and France. For diverse and very important contributions, FB would like to thank Julian Faivovich, Ezequiel Vera, Daniel Udrizar, Carolina Vieytes, Gustavo Simoes Libardi, Franck Barbiere, Martín Ramirez, Mónica Buono, Gastón Martínez, Damián Pérez, Nacho Escapa, José Cuitiño, Santiago Bessone, Andrés Bilmes, Alicia Álvarez, Pablo Teta, María Encarnación Pérez, Michelle Arnal and Raúl Gómez. Aluar is thanked for the photographs included in this article. IPGP and the CENPAT are thanked for their support over the years. FB would also like to thank his family and friends for support during his PhD, and Mariana Viglino for invaluable help and suggestions. The owners of ‘El Molino’ are thanked for granting access to their property for fossil prospecting. Fieldwork was conducted under permits from Secretaría de Cultura, Chubut Province. Two reviewers and the editor are thanked for suggestions that considerably improved the manuscript. Finally, FB would like to thank the Argentinian public educational and scientific systems (especially Universidad de Buenos Aires and CONICET) for access and funding during his PhD. This contribution was financially supported by Sociedad Argentina para el Estudio de Mamíferos (SAREM) to FB; a CONICET doctoral fellowship to FB; CONICET PIP 11220150100113 to MTD; and CONICET PIP 112201500100423 to IMS.

Supplemental material

Supplemental material for this article can be accessed here: http://dx.doi.org/10.1080/14772019.2020.1796833.

Associate Editor: Zerina Johanson