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

<p><span>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 (<em>Prospaniomys</em> <em>priscus</em>) 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. <em>Prospaniomys</em> 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 <em>Prospaniomys</em> 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. </span></p>