Evolutionary trends in terror birds´ (Aves, Cariamiformes) brain anatomy

RIDGELY, R.; TAMBUSSI, C.P.; DEGRANGE, F.J.; WITMER, L.

Diamante

Congreso; 9th International Meeting of the Society of Avian Paleontology and Evolution; 2016

Society of Avian Paleontology and Evolution

Terror birds (Cariamiformes, Phorusrhacidae) are a completely extinct group of ground birds that comprise one of the most remarkable and diverse groups of the South American Cenozoic avifauna. Widely considered to have been apex predators, their basic habitus of being running predators has never been questioned for most of their species. A crucial component of research on Cariamiformes brain evolution is the endocasts comparisons between seriemas and the highly derived Phorusrhacidae. Using virtual reconstructions based on computed tomographies, we assess the morphological features of the virtual endocast of Cariamiformes in order the point out the major transitions in the evolution of terror birds´brain. In a comparative and evolutionary context, features of the endocast suggest that: (1) enlargement of the brain in relation to body size, (2) lateral dimension of the telencefalon increase, (3) enlargement of the wulst, (4) flocculi reduction, (5) optic lobes compared reduction, (6) small enlargement of the olfactory bulb, (7) elongation of the hypophysis and common carotid, and (8) elongation of the crus communis of the inner ear, characterizes the evolutionary transition between seriemas and phorusrhacids. These trends based on neuroanatomical structures indicates a specialization on active predatory skills: prey detection was based on vision, and pursuit was agile, sudden, and through fast movements allowing terror birds to chase and subdue prey.