New information on the braincase and endocranial morphology of the Late Triassic neotheropod Zupaysaurus rougieri using Computed Tomography data

PAULINA CARABAJAL, A.; EZCURRA, M.; NOVAS, F.

JOURNAL OF VERTEBRATE PALEONTOLOGY

SOC VERTEBRATE PALEONTOLOGY

Lugar: Lawrence; Año: 2019 vol. 39 p. 1 - 15

0272-4634

Zupaysaurus rougieri is an early neotheropod from the middle Norian Los Colorados Formation of northwestern Argentina represented by an almost complete skull and several postcranial bones. Most of its braincase morphology remained obscured by other skull bones and sediment. Additional mechanical preparation and X-ray Computed Tomography on the single known specimen of Zupaysaurus has allowed a detailed description of the braincase, cranial endocast, and inner ear of this Triassic dinosaur. Basal theropod braincases are poorly sampled and there is little information on braincase and even poorer knowledge on brain and inner ear anatomy of Triassic forms. The virtual reconstruction of the braincase shows anteroventrally oriented finger-like basipterygoid processes, elongate and horizontally projected cultriform process, and well developed preotic pendant, basisphenoid recess, and subsellar recess. The endocranial morphology is partially reconstructed showing an anteroposteriorly short but dorsoventrally tall cranial endocast with well-marked demarcation between the hindbrain and midbrain, and midbrain and forebrain. The inner ear preserves the three semicircular canals, but not the lagena. The posterior semicircular canal is proportionally large when compared to other theropods. The new information presented here on Zupaysaurus rougieri contributes to the knowledge of  the neuroanatomy of basal theropods, and sheds light on the evolutionary patterns of the  braincase morphology in non-avian Theropoda.