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Evolutionary origins of avian brain



From: Ben Creisler
bcreisler@gmail.com

A new online paper in Nature:


Amy M. Balanoff, Gabe S. Bever, Timothy B. Rowe & Mark A. Norell (2013)
Evolutionary origins of the avian brain.
Nature (advance online publication)
doi:10.1038/nature12424
http://www.nature.com/nature/journal/vaop/ncurrent/full/nature12424.html

Features that were once considered exclusive to modern birds, such as
feathers and a furcula, are now known to have first appeared in
non-avian dinosaurs. However, relatively little is known of the early
evolutionary history of the hyperinflated brain that distinguishes
birds from other living reptiles and provides the important
neurological capablities required by flight. Here we use
high-resolution computed tomography to estimate and compare cranial
volumes of extant birds, the early avialan Archaeopteryx
lithographica, and a number of non-avian maniraptoran dinosaurs that
are phylogenetically close to the origins of both Avialae and avian
flight. Previous work established that avian cerebral expansion began
early in theropod history and that the cranial cavity of Archaeopteryx
was volumetrically intermediate between these early forms and modern
birds. Our new data indicate that the relative size of the cranial
cavity of Archaeopteryx is reflective of a more generalized
maniraptoran volumetric signature and in several instances is actually
smaller than that of other non-avian dinosaurs. Thus, bird-like
encephalization indices evolved multiple times, supporting the
conclusion that if Archaeopteryx had the neurological capabilities
required of flight, so did at least some other non-avian
maniraptorans. This is congruent with recent findings that avialans
were not unique among maniraptorans in their ability to fly in some
form.