First virtual endocast description of an early Miocene representative Pan-Octodontoidea (Caviomorpha, Hystricognathi) and considerations on the early brain evolution in South American rodents

The study of the cranial endocast provides valuable information to
understand the behavior of an organism since it coordinates sensory
information and motor functions. In this work, we describe for the first
time the anatomy of the encephalon of an early Miocene pan-octodontoid
caviomorph rodent (Prospaniomys priscus) found in the Argentinean
Patagonia, based on virtual 3D endocast. This fossil rodent has an
endocast morphology here considered ancestral for Pan-Octodontoidea and
also other South American caviomorph lineages, such as an encephalon with
anteroposteriorly aligned elements, mesencephalon dorsally exposed,
well-developed vermis of the cerebellum, rhombic cerebral hemispheres with
well-developed temporal lobes. Prospaniomys also has relatively small
olfactory bulbs, large paraflocculi of the cerebellum, low endocranial
volume, and a degree of neocorticalization. Its EQ is lower compared with
Paleogene North American and European non-caviomorph rodents, but slightly
higher than several late early and late Miocene caviomorphs. The
paleoneurological anatomical information supports the hypothesis that
Prospaniomys was a generalist caviomorph rodent with terrestrial habits,
and enhanced low-frequency auditory specializations. The scarce
paleoneurological information indicates that several endocast characters
in caviomorph rodents could change with ecological pressures. This work
sheds light on the anatomy and evolution of several paleoneurological
aspects of this particular group of South American rodents.