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Rapid Rates of Evolution across the Dinosaur-Bird Transition

Ben Creisler

A new online paper:

Stephen L. Brusattee, Graeme T. Lloyd, Steve C. Wang & Mark A. Norell (2014)
Gradual Assembly of Avian Body Plan Culminated in Rapid Rates of
Evolution across the Dinosaur-Bird Transition.
Current Biology (advance online publication)
DOI: http://dx.doi.org/10.1016/j.cub.2014.08.034


•A new phylogeny of birds and their closest dinosaur relatives is presented
•Birds evolved anatomical features faster than other theropods
•Birds are indistinguishable from their closest relatives in morphospace
•The assembly of the avian body plan unlocked great evolutionary potential


The evolution of birds from theropod dinosaurs was one of the great
evolutionary transitions in the history of life. The macroevolutionary
tempo and mode of this transition is poorly studied, which is
surprising because it may offer key insight into major questions in
evolutionary biology, particularly whether the origins of evolutionary
novelties or new ecological opportunities are associated with
unusually elevated “bursts” of evolution. We present a comprehensive
phylogeny placing birds within the context of theropod evolution and
quantify rates of morphological evolution and changes in overall
morphological disparity across the dinosaur-bird transition. Birds
evolved significantly faster than other theropods, but they are
indistinguishable from their closest relatives in morphospace. Our
results demonstrate that the rise of birds was a complex process:
birds are a continuum of millions of years of theropod evolution, and
there was no great jump between nonbirds and birds in morphospace, but
once the avian body plan was gradually assembled, birds experienced an
early burst of rapid anatomical evolution. This suggests that high
rates of morphological evolution after the development of a novel body
plan may be a common feature of macroevolution, as first hypothesized
by G.G. Simpson more than 60 years ago.

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