Neuroanatomy of a pterosaur from the Jurassic of Patagonia using Computarized Tomography

PAULINA CARABAJAL, A.; RAUHUT, O.; CODORNIÚ, L.

Las Vegas

Congreso; Society of Vertebrate Paleontology annual meeting; 2011

University of Nevada

The neuroanatomy of pterosaurs is known from very few 3D preserved braincases. We describethe endocranial anatomy and inner ear of a new pterosaur from the Middle Jurassicof the Cañadón Asfalto Formation, Chubut Province, Argentina. The endocast has a volumeof approximately 1.2 ml and has the generalized morphology described for the other knownpterosaur brains, being bulbous, with short olfactory tract and bulbs, cerebral hemisphereswith 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 posterodorsalsection of the hind-brain, and are clearly related with the optical lobes areas. Comparisonswith the brains of Ramphorhynchus and Anhanguera reveal a mosaic of characters in the Argentineanspecimen, which shares some traits with both taxa, but also has intermediate statesfor 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 incomparison with the endocranial cavity. The anterior semicircular canal is markedly largerthan the other two canals and is located dorsal to the posterior canal. The anterior and posteriorsemicircular canals form an angle of 94 degrees. The position of the lateral semicircularcanal suggests that the long axis of the skull roof remained horizontal in life, as in Rhamphorhynchus.The CT scans also reveal some aspects of the pneumaticity of the braincase, whichaffects the paired frontals, supraoccipital, and basisphenoid, including the presence of welldeveloped tympanic pneumatic cavities.