Novel information on the braincase morphology of Gasparinisaura cincosaltensis (Dinosauria, Ornitischia) based on CT scans

PAULINA CARABAJAL, A.; CRUZADO-CABALLERO, P.; CALVO, J.O.

Rincón de los Sauces

Simposio; 1 Reunión de Paleovertebrados de la Cuenca Neuquina; 2017

Museo Argentino Urquiza

The complete skull of the type specimen of Gasparinisaura cincosaltensis (MUCPv-208) -a small ornithopod from the Upper Cretaceous of Argentina- was CT scanned using a medical tomographer. The markedly small size of the skull plus the lateromedial deformation prevented the observation of the endocranial cavity in the CT data set, and further neuroanatomy studies. However, the braincase was virtually ?extracted? from the articulate skull, allowing the first osteological description of this region of the skull for the species. The braincase is narrow, anteroposteriorly short and tall; the ethmoidal complex and orbitosphenoids are unnossified elements. The basicranium is massive, dorsoventrally depressed and anteroposteriorly long. There are no pneumatic recesses. Previously unknown characters include: unnossified ethmoidal elements; ossified laterosphenoid with finger-shaped and laterally projected postorbital processes; paroccipital process short and posteroventrally oriented; well-developed crista prootica; basal tubera poorly differentiated from the main body of the basicranium, basipterygoid processes finger-shaped and lateroventrally projected, with the distal end slightly curved posteriorly; rod-like cultriform process, anteriorly projected. Cranial nerves V and VII were identified. A large depression at the base of the basipterygoid process may correspond to the internal carotid artery. The braincase morphology of basal ornithopods is poorly known and a few numbers of species were described worldwide. The basicranium of Gasparinisaura is similar to that of Dysalotosaurus lettowvorbecki Virchov 1919, from the Jurassic of Africa. The new anatomical information is important because adds novel information to the Argentinean species, and also has potential use in the taxonomy, phylogeny and paleoneurology of the clade.Project funded by PIP 0733 and PICT 2015-0920 (APC); UNCo: 04/I082 and Chevron SA (JOC)