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Rutger Jansma wrote:
Isn't this just logical? I mean...when you reduce the forelimbs before you
increase the relative size of the skull and other changes in the structure
of the skull, you got a theropod can't do anything well.
I'm not so sure it's "logical". Certain other large theropods also show a
reduction in relative forelimb length (e.g., carnotaurines and to a lesser
extent torvosaurids), as well as certain small theropods (e.g.,
compsognathids, alvarezsaurids, caudipterygids, _Shanyangosaurus_?). In
these cases the reduction in forelimb length may not be correlated with a
relative increase in size of the skull. In tyrannosaurids there is
biomechanical evidence that the skull took on a greater role in seizing prey
at the expense of the forelimbs, which were reduced toward a more limited
(but perhaps necessary) function. This evolutionary trajectory is backed up
by the morphologies of _Dilong_ and _Eotyrannus_. For other small-armed
theropods, the adaptive rationale behind reduction of the forelimbs needs
more biomechanical studies, and corroboration from the fossil record.
_Dilong_ also shows that tyrannosaurids had a tridactyl manus *before* the
forelimbs were truncated.
- Re: Dilong
- From: fam jansma <email@example.com>