Endocranial Cast Anatomy of the Extinct Hipposiderid Bats Palaeophyllophora and Hipposideros (Pseudorhinolophus) (Mammalia: Chiroptera)

Abstract

Bat fossil endocasts have been little studied in the literature (nine published works, only one in the XXIth century), and macromorphology of the brain of extant bats has only been characterized at the family-level. We describe here in detail the endocranial casts of four fossil hipposiderid species based on μCT-scans data and propose a revised nomenclature of the hipposiderid brain structures that leave their imprint on endocranial casts. Exhaustive comparisons of the external morphology of our fossil cranial endocast sample allow us to discuss the distribution of both qualitative and quantitative features in this family for different epochs. A conservatism of the brain is considered to be the rule during bats evolution. Indeed, we found that encephalization did not increase since the Eocene in hipposiderid bats (contrary to other mammals) and that macromorphology of the brain is close between Paleogene, Miocene, and extant hipposiderid species. However, subtler but promising fine anatomical characters might allow distinguishing genera and species. Eventually, expanding the fossil sample and/or adding extant species could shake the paradigm of temporal homogeneity and bring new light on the morpho-anatomical evolutionary history of Hipposideridae.