Meeting Abstract

29.3  Saturday, Jan. 4 14:00  The Deep History of the Avian Brain BALANOFF, A.M.; Stony Brook University School of Medicine amy.balanoff@stonybrook.edu

Many of the characters that have historically been associated with living birds, crown group Aves, such as a feathers and a furcula and even behaviors like brooding nests of eggs are now known to have originated much deeper in the evolutionary history of the lineage than previously thought, among non-avian dinosaurs. An earlier origin also looks to be the case for the evolution of the avian brain. Volumetric analyses of the endocranium along the avian lineage reveal that a “bird-like” brain first appears early within maniraptoran dinosaurs, yet the morphology of the brain within this group, which includes living birds, has yet to be assessed. A modern bird brain exhibits a suite of characters that vary little across the avian tree. Such characters include but are not limited to laterally displaced optic lobes, retracted olfactory tracts and reduced bulbs, an enlarged cerebrum with a prominent sagittal eminence, and folded cerebellum. Using endocranial renderings derived from CT data of fossil and extant taxa, I examined the distribution of these and other characters along the entire maniraptoran lineage. Consistent with other character systems, most “bird-like” features of the brain are not restricted to the crown group but have a much longer evolutionary history. Furthermore, relatively few characters now diagnose the avialan clade. Instead, the base of Avialae as exemplified by the stem bird Archaeopteryx lithographica exhibits a generally plesiomorphic morphology that can be diagnosed by characters shared with maniraptorans and paravians.