Neuroanatomy of a diplodocid sauropod dinosaur from the Lower Cretaceous of Patagonia, Argentina

Diplodocid neuroanatomy is known from four Late Jurassic forms from North America and Africa. Recently, a partial braincase of a diplodocid sauropod (MMCh-Pv-232), tentatively assigned to Leinkupal laticauda Gallina et al., 2014, preserving a complete basicranium, right laterosphenoid, prootic, parietal, otooccipital and right half of the supraoccipital, was recovered from Bajada Colorada Formation (Ber-riasian-Valanginian). Reconstructions of the braincase, cranial endocast and inner ear were performed via X-ray Computed Tomography and segmentation. The endocast is represented by the pituitary body (inclined at 69 degrees from the base of the medulla oblongata-similar to Diplodocus), the caudal-most region of the cerebral hemispheres and the internal carotid arteries, the midbrain, showing Cranial Nerve (CN) III and CN IV exiting the braincase through a single opening; and the hindbrain, with CN V exiting the braincase through a single opening as in other sauropods, the ventral CN VI entering the pituitary fossa caudally, CN IX-XI exiting the braincase through a single opening (metotic foramen), and CN XII exiting the braincase through two canals. The inner ear preserved a caudoventrally inclined conical lagena, a sub-rectangular fenestra ovalis, the ampulla of the Anterior Semicircular Canal, the crus commune, and a Lateral Semicircular Canal. The length of the lagena suggests a lower auditive capacity in comparison to other sauropods. The morphological similarities of the braincase and endocast to other diplodocids reinforce the tentative assignation of MMCh-Pv-232 to Leinkupal, and expands the knowledge in neuroanatomy of South American sauropods. (c) 2021 Elsevier Ltd. All rights reserved.