Abstract

CARABAJAL, Ariana Paulina  and  SALGADO, Leonardo. A titanosaur (Dinosauria, Sauropoda) braincase from the Upper Cretaceous of North Patagonia: description and contribution to the knowledge of the dinosaur inner ear. Ameghiniana [online]. 2007, vol.44, n.1, pp.109-120. ISSN 1851-8044.

The braincase of a sauropod dinosaur from the Upper Cretaceous of Río Negro, Argentina, is described. The material is assigned to the clade Titanosauria and some characters that resemble the condition present in the genus Antarctosaurus such as the presence of short and wide frontals and parietals, supraoccipital knob lacking a medial groove, reduced and dorsally exposed supratemporal fenestrae, frontals fused on the midline, and a single interfrontal medial knob are discussed. These characters are not diagnostic and they can be found in other titanosaurs such as Rapetosaurus, Nemegtosaurus, Saltasaurus and Bonatitan. The braincase, although incomplete, is well preserved, allowing the examination of certain delicate internal structures like the inner ear, which has been exposed through bone fractures. The titanosaurian inner ear is described here for the first time: it is morphologically similar to that of other sauropods such as Diplodocus and Brachiosaurus, mainly in the spatial disposition of the semicircular canals, although showing a proportionally more robust lagena. The angle between the planes on which the anterior and posterior semicircular canals lie is greater than 90º, as in other herbivorous dinosaurs, and different from the theropod Allosaurus, where that angle is smaller.

Keywords : Titanosauria; Braincase; Inner ear; Upper Cretaceous; Patagonia.