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A duo of new papers on terrestrial locomotion in extant birds (with
comments on non-avian theropod locomotion) is out (Wow, J. Morph. is pretty
Gatesy, SM. 1999a. Guineafowl hind limb function. I: Cineradiographic
analysis and speed effects. J. Morphology 240:115-125.
Consists of the first published x-ray cine analysis of neornithine
striding bipedal locomotion, with accurate measurements of joint angle
changes. Makes the point that some "avian" kinematic features are primitive
within theropods, but on the other hand not all features of modern
bipedalism in birds are primitive to all theropods. Blows away some
earlier assertions (e.g. Campbell and Marcus 1992 in the Brodkorb volume)
that neornithine limb joint excursions do not change with speed.
Gatesy, SM. 1999a. Guineafowl hind limb function. II: Electromyographic
analysis and motor pattern evolution. J. Morphology 240:127-142.
EMG analysis of 16 heads of 14 muscles and their implications for
kind limb muscle function and neuromotor evolution. From abstract: "Most
novelties in extant saurian motor patterns arose on the line to living
birds." (i.e. data from lizards and crocodilians suggest that they mostly
retain plesiomorphic EMG patterns.) Another nail in the coffin for the old
practice of inferring muscle function from morphology alone.
If you're even slightly interested in avian bipedalism or muscle function
you'll need these refs.
--John R. Hutchinson