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Re: Archaeopteryx or Velociraptor (I'm back...)...



In a message dated 97-07-04 06:14:13 EDT, thelip@flash.net (Sean Connell)
writes:

<< And isn't it true that Tyrannosaurids might be secondarily
 cursorial?-Sean C. >>

I don't know about "true," but my personal best guess is that this is the
case. I envision the common ancestor of Tyrannosauria as a volant
maniraptoran similar in overall appearance to _Archaeopteryx_ but perhaps
smaller in overall size, with wings having only two functional digits, the
third being vestigial or entirely absent. So this would make tyrannosaurians
secondarily cursorial.

For a while, it seemed to me as if Compsognathus, with its two-digit
forelimbs, was close to tyrannosaurian ancestry, but now I'm not quite so
sure. Too many compsognathid-like dinosaurs (Sinosauropteryx, unnamed Italian
form) are turning up with three-digit forelimbs, making it more likely that
these digits are just missing from the specimens, not absent from the animal.
Also, compsognathid feet are not arctometatarsalian, which would mean
tyrannosaurians developed arctometatarsalian feet convergently with certain
other cursorial theropods. But it remains odd that the digits with the
largest number of joints, from both hands, in both specimens of
Compsognathus, would be completely missing, whereas the other digits are well
represented.