Paleoneuroanatomy of a new riojasaurid (Dinosauria: Sauropodomorpha) of the Late Triassic of Argentina

MARTINEZ, RICARDO NESTOR; APALDETTI, CECILIA; PAULINA CARABAJAL, ARIANA

Congreso; SVP Meeting; 2019

Here, we present the first paleoneurological study based on CT scans of the skull of a new riojasaurid sauropodomorph (PVSJ 849) from the Los Colorados Formation (Late Triassic) of Argentina . The CT scan allowed the rendering of the braincase and endocranial cavities, resulting in the most complete anatomical data for a South American representative of the clade. The cranial endocast of PVSJ 849 characterizes by a low dorsal expansion, cerebral hemispheres poorly expanded laterally, elongated olfactory tract and bulbs, presence of flocculus of the cerebellum, and bulbous and short pituitary. The cranial endocast has a marked sigmoidal shape in lateral view, the olfactory bulbs are aligned with the forebrain, the midbrain is posteroventrally inclined and the hindbrain is parallel and ventral to the forebrain. The flocculus is relatively large, similar in size to that in Saturnalia tupiniquim and basal Neotheropoda, but unlike the small flocculus in Plateosaurus sp. The inner ear has slender semicircular canals, and the relative size of anterior, posterior and lateral semicircular canals are similar to S. tupiniquim. In dorsal view, the angle formed between anterior and posterior semicircular canals is about 80 degrees. The brain, cranial nerves and inner ear of few Carnian dinosaurs have been studied, and within South American taxa these include only S. tupiniquim from Brazil. The preliminar comparisons suggests a primitive condition within Riojasauridae, with a neuroanatomy more closely related to the most basal forms as S. tupiniquim than those more derived Triassic basal sauropodomorphs as Plateosaurus sp.