The rostral neurovascular system of Tyrannosaurus rex

The study of the rostral neurovascular system using CT scanning has shed new light on phylogenetic and palaeobiological reconstructions of many extinct tetrapods. This research shows a detailed description of the rostral neurovascular canals of Tyrannosaurus rex including the nasal, maxillary (dorsal alveolar), and mandibular (ventral alveolar) canals. Extensive comparisons with published descriptions show that the pattern of these canals in Tyrannosaurus is not unusual for a non-avian theropod. As in the non-avian theropod Neovenator, the maxillary canal shows several anastomoses of its branches. Differences from the plesiomorphic sauropsid condition are concentrated within the canal for the maxillary neurovasculature, which is primitively horizontal, tubular, and connected to a single row of supralabial foramina, whereas in Tyrannosaurus the main trunk of the canal is oriented more obliquely and dorsally displaced to give room to the deep tooth alveolae. As a result, the lateral branches that provide innervation and blood supply to the skin are dorsoventrally elongated compared to non-theropod taxa, and multiple rows of supralabial foramina are present. An overview of the literature suggests that the evolution of the trigeminal canals among sauropsids only weakly supports previous hypotheses of crocodile-like facial sensitivity in non-avian theropods (except, maybe, in semiaquatic taxa). More systematic studies of the rostral neurovascular canals in non-avian theropods may help answer the question of whether lips were present or not. Florian Bouabdellah. Universities of Poitiers, 15 Rue de l'Hôtel Dieu, TSA 71117, 86000 Poitiers, France. [email protected] Emily Lessner. University of Missouri School of Medicine, Columbia, MO, 65211, USA. [email protected] Julien Benoit. Evolutionary Studies Institute and School of Geosciences, University of the Witwatersrand, Johannesburg 2050, South Africa, [email protected]