Meeting Abstract

45.6  Sunday, Jan. 5 11:30  From Archaeopteryx to modern Aves: testing the impact of allometry and phylogeny in shaping bird brain evolution WATANABE, A.*; BALANOFF, A.B.; NORELL, M.A.; American Museum of Natural History, New York; Stony Brook University, Stony Brook; American Museum of Natural History, New York awatanabe@amnh.org

Brain anatomy is thought to be highly reflective of the major functional abilities of an organism, such as locomotory mode. Among birds (Aves), this association implies that the disparate morphological and ecological factors underpinning flight performance may correspond to specific brain morphologies. Yet, recent findings spanning volant and non-volant birds and mammals suggest that neuroanatomy (e.g., relative lobe size and shape) is not directly concomitant with flight performance. Instead, these results point to other possible drivers of morphological and functional evolution of the avian brain. Here we integrate three-dimensional geometric morphometric approaches and comparative phylogenetic methods to test whether allometry and phylogeny account for shape variation in this system. Digital endocranial models were constructed from CT-scanned images of over 20 species, including Archaeopteryx, broadly sampling the ecological, phylogenetic, and size ranges of Aves. Landmark and semi-landmark points were then digitally mapped to model surfaces to characterize the morphology. Our data show that neither phylogeny nor size alone significantly accounts for brain shape in birds. These results imply that brain evolution along the avian line has been guided by a more complex interplay of selective factors than previously realized. Additional considerations, such as social behavior or constraints of skull morphology, should be tested in the future to better elucidate this evolutionary problem.