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New paper- Evolutionary origins of the avian brain



>From today's issue of nature magazine. Perhaps of interest.

Evolutionary origins of the avian brain

Amy M. Balanoff,     Gabe S. Bever,     Timothy B. Rowe     & Mark A. Norell
AffiliationsContributionsCorresponding author
Nature 501, 93­96 (05 September 2013) doi:10.1038/nature12424
Received 10 March 2013 Accepted 24 June 2013 Published online 31 July 2013
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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
dinosaurs1. 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 flight2. 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 birds3, 4.
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
form5, 6.