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Re: More Holtz on the origin of birds



In a message dated 95-12-07 12:10:26 EST, Thomas_R_HOLTZ@umail.umd.edu (th81)
writes:

>Despite endless usage in ornithological textbooks everywhere, there is NO
>(count them, No) major trend towards arm reduction within theropod
>evolution.  A few lineages (advanced megalosauroids, neoceratosaurs,
>tyrannosaurids, and Compsognathus) had reduced arms (shortened fore arms in
>the first two, reduced as a whole in the second).  Among the remaining
>groups of theropods, arms were of moderate (Coelophysoidea, Carnosauria) or
>long (Coelurosauria) length.

Technically, Tom is correct. What is reduced is the ratio of forelimb to
hindlimb length; so you can think of this as the hindlimbs becoming longer
rather than the forelimbs becoming shorter. Naturally, I prefer to think of
this as the body and hind limbs becoming larger and the forelimbs falling
behind.