Morphology of cheek teeth and dental replacement in the extinct rodent Neoepiblema Ameghino, 1889 (Caviomorpha, Chinchilloidea, Neoepiblemidae)

ABSTRACT

Neoepiblemidae (Caviomorpha) includes South American hystricognath rodents that together with Chinchillidae and Dinomyidae compose the clade Chinchilloidea. Despite the considerable advance in knowledge of the past decades, these extinct rodents are still poorly studied. To contribute to the taxonomy, systematics, and ontogeny of this group, in this paper we study the cheek tooth morphology of the genus Neoepiblema Ameghino, 1889, from upper Miocene deposits through qualitative and quantitative analyses. For this purpose, we describe the anatomical variation, perform a quantitative analysis using linear measurements, and provide comments on the dental replacement. Based on the cheek tooth morphology, our interpretations indicate that there are two species of Neoepiblema that can be differentiated from each other. Neoepiblema ambrosettianus is not a valid name, and N. horridula, the first described Neoepiblema species, is the senior synonym. Hence, N. acreensis is a valid name for the second species of the genus. In neoepiblemids, the premolar is replaced during the early postnatal period, similar to euhypsodont dinomyids and in contrast to some other euhypsodont caviomorphs (e.g., cavioids), which replace the premolar during the intrauterine stage. These data on dental replacement in neoepiblemids contribute to knowledge about the ontogeny of this extinct rodent group.

ACKNOWLEDGMENTS

We thank CNPq (Conselho Nacional de Pesquisa e Tecnologia) (processes 163168/2014-8, 201356/ 2015-5) and FAPERGS (Fundação de Amparo à Pesquisa do Rio Grande do Sul (process 17/2551-0000816-2) (to L.K.) for funding; the UFAC team (A. Maciente, A. Ranzi, E. Guilherme, J. Bocquentin-Villanueva, J. C. R. dos Santos, J. P. Souza-Filho, among others) that collected the studied material housed in UFAC; A. Kramarz and S. Alvarez (MACN) and M. Reguero (MLP) for access to the collections under their care; UFSM, for the infrastructure provided; K. Piper for the review of grammar; and both reviewers for their suggestions, which help us to improve the manuscript.

ORCID

Leonardo Kerber http://orcid.org/0000-0001-8139-1493

Note

After the submission of the last version of this article, a study was published on the homology of chinchilloid teeth, including neoepiblemids: Rasia, L. L., and A. M. Candela. 2019. Upper molar morphology, homologies and evolutionary patterns of chinchilloid rodents (Mammalia, Caviomorpha). Journal of Anatomy 234, 50–65.