An Overview on the Crocodylomorpha Cranial Neuroanatomy: Variability, Morphological Patterns and Paleobiological Implications

Abstract

An overview of the neuroanatomy and the principal anatomical transformations of the cranial endocast of the main lineages of Crocodylomorpha are presented. One of the main transformations of the cranial endocast within pseudosuchians seems to be the lateral extension of the cerebral hemispheres, occurred near the node Crocodyliformes and interpreted as a reversal in thalattosuchians and dyrosaurids to cranial endocast with narrow cerebral hemispheres. Relatively larger cerebral hemispheres indicate greater processing of environmental information and more complex responses. Prominent olfactory bulbs and expanded optic lobes of several terrestrial notosuchians are linked to greater olfactory acuity and visual capacity. Inner ear morphology is mostly conservative in Crocodylomorpha; however, the vestibulum and lagena are dorsoventrally short in Almadasuchus and aquatic crocodyliforms. Relative sizes of the trigeminal fossa and maxillomandibular foramen showed an increase in size along the line to amphibious crown crocodylians, contrasting with putatively terrestrial crocodyliforms as protosuchids and several notosuchians, further suggesting that somatosensation evolved later in the group than previously proposed (but depending on the phylogenetic position of thalattosuchians). Neuroanatomical information at the base of Crocodylomorpha-Crocodyliformes and within Mesoeucrocodylia is relatively scarce, but crucial to understanding the neurological novelties developed by the group in terrestrial and aquatic environments.