Neuroanatomy of Gryposuchus neogaeus (Crocodylia, Gavialoidea): a first integral description of the braincase and endocranial morphological variation in extinct and extant gavialoids

BONA, P.; PAULINA CARABAJAL, A.; GASPARINI, Z.

EARTH AND ENVIRONMENTAL SCIENCE TRANSACTIONS OF THE ROYAL SOCIETY OF EDINBURGH

ROYAL SOC EDINBURGH

Lugar: Edinburgo; Año: 2017 vol. 106 p. 235 - 246

1755-6910

Morphological studies of the braincase and cranial endocast of fossilcocodylians, especially gavialids, are scarce. Here we present a detaileddescription of the neuroanatomy of Gryposuchus neogaeus from the Mioceneof Argentina based on CT scans. The cranial endocast is sub-horizontal and theangle formed between the mid-brain and the hind-brain is poorly marked. Whencompared with Gavialis gangeticus, the mid-brain of G. neogaeusis relatively shorter, although the distribution of cranial nerves is similar. Inthe floor of the endocranial cavity, posterior the dorsum sellae, there is amedian foramen that leads into a canal that runs anteroventrally through thebasisphenoid to penetrate the posterior wall of the pituitary fossa (openforamen for the basilar artery?). The same structure is present in G.gangeticus but is absent in other living crocodylians, suggesting aparticular character of Gavialoidea. The pneumaticity of the skull roof and thelateral branches of the pharingotympanic system in G. neogaeus aremarkedly reduced when compared with the extant species. Comparisons with theliving Gavialis indicate that the pattern of braincase morphology ofGavialidae was present in the Miocene; however, the internal morphology,including brain shape, pneumaticity of the skull roof and basicranium isdifferent in the two species. This work is the first step tounderstand the variation of the neuroanatomy in this group ofarchosaurs and it paleobiological implication.