Neuroanatomy of a pterosaur from the Jurassic of Patagonia using computarized tomography

PAULINA CARABAJAL, A.; RAUHUT, O.W.; CODORNIÚ, L.S.; POL, D.

Las Vegas

Congreso; 70th Meeting of the Society of Vertebrate Paleontology; 2011

Society of Vertebrate Paleontology

The neuroanatomy of pterosaurs is known from very few 3D preserved braincases. We de- scribe the endocranial anatomy and inner ear of a new pterosaur from the Middle Jurassic of the Cañadón Asfalto Formation, Chubut Province, Argentina. The endocast has a volume of approximately 1.2 ml and has the generalized morphology described for the other known pterosaur brains, being bulbous, with short olfactory tract and bulbs, cerebral hemispheres with large optic lobes that are ventrolaterally displaced, and an extremely enlarged flocculus. The dorsal head veins enter the longitudinal sinus, forming two horns on the posterodorsal section of the hind-brain, and are clearly related with the optical lobes areas. Comparisons with the brains of Ramphorhynchus and Anhanguera reveal a mosaic of characters in the Ar- gentinean specimen, which shares some traits with both taxa, but also has intermediate states for other characters. The disposition of several cranial nerves can be traced on the endocast. The three semicircular canals of the inner ear are preserved. They are remarkably large in comparison with the endocranial cavity. The anterior semicircular canal is markedly larger than the other two canals and is located dorsal to the posterior canal. The anterior and poste- rior semicircular canals form an angle of 94 degrees. The position of the lateral semicircular canal suggests that the long axis of the skull roof remained horizontal in life, as in Rhampho- rhynchus. The CT scans also reveal some aspects of the pneumaticity of the braincase, which affects the paired frontals, supraoccipital, and basisphenoid, including the presence of well developed tympanic pneumatic cavities.