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At 11:38 PM 6/29/98 -0400, you wrote:
>Again, I do not wish to get too deep into this for time reasons. But
        Understandable (I really don't have time to give this subject the
attention it deserves, and I'm not writing any books :)

>arboreality does not well explain the large sternal plates seen in small
>advanced theropods.
        Or, for that matter, the small sternal plates seen in large advanced
theropods, but that's another story...

>For two reasons. First, climbers do not have such large
>bird-like plates.
        Ok. How many non-avian climbers are the descendants of obligate
bipeds? Could there be differences associated with the different locomotory
style? I can't (offhand) think of anything that would move remotely like a
theropod when in a tree, so I'm not sure how applicable your generalization is.
        Anyway, I'm not sure I can see exactly why large pectoralis muscles
would be needed by anything with a posterior-facing glenoid in the first place. 

>Next, arboreal animals tend to have reduced(!) limb muscles
>(Grand 1977), so they do not need large sterna.
        Again, how applicable is this data to theropods? Given the
restricted range of motion for the hindlimbs, is it possible that the
forelimbs were required to pull extra duty (as it were) when the animals fell?

>Increased attachment area for flight muscles,
        How big are the sterna of modern flightless birds? I honestly do not
have a clue myself (nor a reference work handy)...

>and increased ventilation of air-sacs needed to sustain flight,
        Or fast running?

>are the best explanations for the large sterna of these theropods. 
        Oh well... Your points are well taken. Thanks
    Jonathan R. Wagner, Dept. of Geosciences, TTU, Lubbock, TX 79409-1053
                    "...To fight legends." - Kosh Naranek