Unravelling the distinctive craniomandibular morphology of the Plio-Pleistocene Eumysops in the evolutionary setting of South American octodontoid rodents (Hystricomorpha)

OLIVARES, A. ITATÍ; ALVAREZ, ALICIA; VERZI, DIEGO H.; PEREZ, S. IVAN; DE SANTI, NAHUEL A.

PALAEONTOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2020 vol. 63 p. 443 - 458

0031-0239

Abstract: Echimyidae is a species-rich clade of Neotropical rodents, which diversified inassociation with forested biomes. A few lineages were adapted to open environments fromsouthern South America since the late Miocene. Eumysops is one of these southernechimyids, and its peculiar craniomandibular morphology has been assumed to be a resultof adaptation to open environments. We performed a geometric morphometric analysis ofcraniomandibular shape variation in order to explore if Eumysops is, as suspected,divergent from other echimyids and octodontoids. In addition, we explored whetherdeterministic factors driven by different ecological dimensions can explain thediversification of shape among octodontoids. We found that craniomandibular shapevariation in octodontoids was related to ecological variables. Comparing competingevolutionary models suggested that the input of selective factors play a key role inoctodontoid craniomandibular shape diversification; habitat and habits were found to bethe most influential factors. In the analysed morphospaces, Eumysops was located distantfrom other echimyids due to its distinctive traits, especially wide and posteriorly displacedorbits, and related low craniomandibular joint. Divergent orbits and resulting widerpanoramic vision support the interpretation of Eumysops as an open-habitat specialistechimyid. But what is more relevant, Eumysops occupied a sector of the octodontoidcranial morphospace not filled by living representatives; this highlights the contribution offossils in providing key information on the specialization boundaries explored by a cladethroughout its history.