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The trend of shortening theropod arms



   Just to throw some water on the recent "shortening of theropod limbs" 
posts:

   From Thom Holtz, about dromaeosaurids....

> --big arms. Theropods in general, from Tyrannosaurs to Carnotaurs,
>have evolved smaller arms. Why the big reversal in Dromaeosaurs?

    [Brace yourself, everyone :-) ] 

    
AAARRRRRRRRRRRRRRRGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGHHHHHHHHHHHHHHH!!!

    Would someone PLEASE kill this bugaboo of an "argument" for me? Thank 
you! 

    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.

    There is NO reversal of arm length in Dromaeosauridae. All of the out 
groups (Oviraptorosauria, Therizinosauroidea, Arctometatarsalia, etc.) 
are characterized primitively by long arms.

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