Endocranial morphology and neuroanatomy of Gryposuchus neogeus (Crocodylia: Gavialoidea)

BONA, P.; PAULINA CARABAJAL, A.

Mendoza

Congreso; International Paleontological Congress; 2014

International Paleontologica Asociation

Here, we present a detailed description of the endocranium and neuroanatomy of Gryposuchus neogeus from the Miocene of Argentina, using CT scans. The braincase and internal morphology were studied. The reconstructed cranial endocast is relatively sub-horizontal and the angle formed between the mid-brain and the hind-brain is poorly marked. When compared with Gavialis gangeticus, the dorsal margin of the endocast of G. neogeus shows that the mid-brain is relatively shorter, although the distribution of cranial nerves is similar. An interesting trait is observed in the floor of the endocranial cavity, posterior the dorsum sellae. There are three small foramina near to the midline, the lateral ones correspond to cranial nerve VI, whereas the median foramen corresponds to a canal that runs anteroventrally through the basisphenoid to penetrate the posterior wall of the pituitary fossa (open foramen for the basilar artery?). The same structure is present in Gavialis but absent in other living crocodilians. The pneumaticity of the skull roof in G. neogeus is markedly reduced, affecting only the parietal; also, the lateral branches of the pharingotympanic system are reduced when compared with the extant species. Preliminary conclusions based on comparisons with the living Gavialis indicate that the pattern of braincase morphology of Gavialidae was present in the Miocene; however, the internal morphology, including brain shape, pneumaticity of the skull roof and basicranium is different in the two species. Morphological studies of the braincase and endocranial morphology of fossil corcodylians, especially gavialids, are scarce. This work is the first step to understand the endocranial morphological pattern and the neuroanatomy variation in this group of archosaurs .