The biological implications of the neurovascular foramina on the abelisaurid nasals

CERRONI, MAURICIO ANDRÉS; CANALE, JUAN IGNACIO; PAULINA CARABAJAL, ARIANA; NOVAS, FERNANDO EMILIO

La Plata

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

Abelisaurids were one of the most successful theropod clades during Cretaceous times. They are featured by numerous derived skull traits such as heavily ornamented bones, short and tall snout, and a strongly thickened cranial roof. Particularly, nasals are distinctive on having two morphotypes; strongly convex (e.g., Carnotaurus Bonaparte, 1985) or concave in transverse section (e.g, Rugops Sereno et al., 2004). No matter which morphotype exhibits, some abelisaurids show over the dorsal surface on each nasal a distinctive row of large foramina. We conducted CT scans on the skulls of Carnotaurus and Skorpiovenator Canale et al. 2008 with the aim of visualize potential internal structures linked to these foramina. The results indicate that they are associated to a single and narrow canal that extends anteroposteriorly across each nasal bone, being notably larger in diameter in Skorpiovenator. The symmetry and lateralized position of these canals and foramina would indicate a neurovascular origin. Regarding vasculature, they may represent branchs of the lateral nasal blood vessels as in extant archosaurs. Whereas, the cranial innervation may corresponds to the ophthalmic branch of the trigeminal nerve (CN V1), which innervates nasals in living crocodiles and birds. Given there isn´t an extant form with an analogue structure, the biological significance of such neurovascular system can be conjectured from several hypotheses. One possibility involves an enhanced blood volume linked to a thermal exchange zone. However, other more speculative explanations like display structures (in which higher blood volumes nourished the mineralized skin) and sensory tissues should not be discarded.