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Another explanation may be that a gizzard laden with gastroliths may put weight
devoted to mechanical food processing below the wings of birds (where it is
beneficial to stability) while the head is lightened by the loss of heavy teeth
and jaws; as opposed to having a heavy head which could be detrimental to
flight. Of course, several theropods apparently utilized gastroliths (beaked
critters: ornithomimids and _Caudipteryx_; and toothy critters:
_Poekilopleuron_, _Nqwebasaurus_, and _Lourinhanosaurus_), so it may have been
more a matter of losing teeth and gaining beak than "adding" a gizzard, which
was probably in place already.
On the other hand, I don't know why gastroliths have been discovered and
described for so few individuals of such a wide array of species (and not just
theropods, obviously). Preservational bias against hard, rounded rocks?
---------Ralph W. Miller III
So you want to be an archosaur? You must have holes in your head!
- From: "Nicholas Jainschigg" <firstname.lastname@example.org>