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

JUAN PABLO GARDERES; PABLO ARIEL GALLINA; JOHN ANDREW WHITLOCK; NÉSTOR TOLEDO

Congreso; Reunión de Comunicaciones de la Asociación Paleontológica Argentina; 2019

Diplodocid neuroanatomy is known from the Upper Jurassic taxa 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; it also preserves the postero-ventral region of the midbrain, preserving the CN-III but not the CN-IV; the hindbrain is slightly wider than in Diplodocus and Apatosaurus, having 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 poor preservation of the material, the inner ear was not possible to be fully reconstructed. Nonetheless, we can recognize a conical lagena, a closely circular fenestra ovalis as in Diplodocus, a subrectangular fenestra pseudorotunda, the sacculus of the ASC, the common trunk between ASC and PSC, and a LSC slightly longer to Diplodocus. The morphological similarities with 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.