Data from: Unravelling the distinctive craniomandibular morphology of the Plio‐Pleistocene Eumysops in the evolutionary setting of South American octodontoid rodents (Hystricomorpha)

Abstract: Echimyidae is a species-rich clade of Neotropical rodents, which
diversified in association with forested biomes. A few lineages were
adapted to open environments from southern South America since the late
Miocene. Eumysops is one of these southern echimyids, and its peculiar
craniomandibular morphology has been assumed to be a result of adaptation
to open environments. We performed a geometric morphometric analysis of
craniomandibular shape variation in order to explore if Eumysops is, as
suspected, divergent from other echimyids and octodontoids. In addition,
we explored whether deterministic factors driven by different ecological
dimensions can explain the diversification of shape among octodontoids. We
found that craniomandibular shape variation in octodontoids was related to
ecological variables. Comparing competing evolutionary models suggested
that the input of selective factors play a key role in octodontoid
craniomandibular shape diversification; habitat and habits were found to
be the most influential factors. In the analysed morphospaces, Eumysops
was located distant from other echimyids due to its distinctive traits,
especially wide and posteriorly displaced orbits, and related low
craniomandibular joint. Divergent orbits and resulting wider panoramic
vision support the interpretation of Eumysops as an open-habitat
specialist echimyid. But what is more relevant, Eumysops occupied a sector
of the octodontoid cranial morphospace not filled by living
representatives; this highlights the contribution of fossils in providing
key information on the specialization boundaries explored by a clade
throughout its history.