NEUROANATOMY OF A DIPLODOCID SAUROPOD DINOSAUR FROM THE LOWERMOST CRETACEOUS OF PATAGONIA

GARDERES, J.P.; GALLINA, P. A.; WHITLOCK, J.A.; TOLEDO, N.

La Plata

Jornada; Reunión Anual de Comunicaciones de la Asociación Paleontológica Argentina; 2019

FCNyM-UNLP

Diplodocid neuroanatomy is known from the upper Jurassic forms Diplodocus Marsh, 1878, Apatosaurus Marsh, 1877 and Tornieria Sternfeld, 1911. Recently, a partial braincase of a diplodocid sauropod (MMChPV- 232), tentatively assigned to Leinkupal laticauda Gallina et al, 2014, lacking the anterior and left latero-dorsal portions of the neurocranium, was reported from Bajada Colorada Formation (Berriasian-Valanginian). A reconstruction of the cranial endocast and inner ear was performed via CT and segmentation. It is represented by the ventral region of the forebrain, only represented by the pituitary body (at 26° from the opening of the CN-VI ?similar to Diplodocus) and the right internal carotid artery, the postero-ventral region of the midbrain, preserving the CN-III but not the CN-IV, and the hindbrain slightly wider than Diplodocus and Apatosaurus, with the CN-V (presenting a single opening, as in other sauropods), the paired ventral CNs-VI, the cranial nerves IX-XI leaving the braincase through the same opening (metotic foramen) and the CN-XII. Due to the general poor preservation of the material, the inner ear was not possible to be fully reconstructed, but a conical lagena, a closely circular fenestra ovalis as in Diplodocus, the sacculus of the ASC, the common trunk between ASC and PSC, and a LSC slightly longer to Diplodocus, are recognized. The morphological similarities to other diplodocids and the absence of diagnostic neuroanatomical characters of dicraeosaurids (the other sauropod group present in the locality), reinforce the tentative assignation to Leinkupal.