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Opisthopuby in Coelurosaurs

tsg94001@uconnvm.uconn.edu wrote:

<Does anybody know why certain theropods (dromaeosaurids, birds,
therizinosauroids) have the pubis pushed back?  I have heard that
ornithischians have an opisthopubic pelvis because it makes space for a
bigger gut (always helpful when digesting cellulose-rich, nutrition-poor
plant matter). This could apply to therizinosauroids too, but why did
dromaeosaurids and birds do it?>

  It could apply to therizinosaurs, who would have adapted the
existing meso- or propubic conditions to develop opisthopuby
(irrelevant of their origins). As for droms and birds, read papers by
Gatesy (1990, 1995) and Gatesy and Biewener (1991). These relate to
the hindlimb musculature shift in shorter tails, shorter femora,
longer tibiae and tarsometatarsi, and stouter backs, all which serve
to do quite a few things. Yes, I'm being vague. Check out the papers.
They should be fairly easy to get. Steve (Gatesy) is on this list, or
was, so he may give a better set of references that don't contain his
name :-).


Gatesy, S.M. 1990. Caudofemoral musculature and the evolution of
theropod locomotion. _Paleobiology_ 16: 170-186.

____________ 1995. Functional evolution of the hindlimb and tail from
basal theropods to birds. pp. 219-234. (in Thomason, J.J. (ed.)
_Functional Morphology in Vertebrate Paleontology_ [Cambridge
University Press]).

____________ and Biewener, A.A. 1991. Bipedal locomotion: effects of
size, speed and limb posture in birds and humans, _Journal of Zoology,
London_ 224: 577-588.

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