dinosaur vs. bird locomotion

[crnoto@midway.uchicago.edu (Chris Noto)]

Recently in my Intro to Paleo course my prof gave an example of theoretical
morphological analysis using the "did dinosaurs walk more like birds or
like mammals?" comparison.  What struck me is that it seems intrinsically
flawed because birds are a highly derived form of one branch of the
therepods and comparing them to, say, a ceretopsian would be like using a
kangaroo rat as a comparison for human locomotion just because we're both
mammals.  Furthermore, even using it as a comparison to non-avian therepods
seemes a little off to me.  Aren't ground dwelling birds (like chickens)
secondarily flightless and have a whole evolutionary history, setting them
apart from their non-avian ancestors?  Then there's the size difference.
No bird ever got that BIG, the scaling could throw it all off then.  You
need to take into account the limits of the material used here (ie, bone).
Could that affect certain proportions in limb length and throw off the
analysis?  I've been thinking about this quite a bit and it just doesn't
seem quite kosher, the differences seem to great.  Isn't that why birds are
set apart from dinosaurs in the first place?  Any thoughts or comments
would be appreciated.

thanks,
Chris Noto

-----------------------------------
Chris Noto
University of Chicago
c-noto@uchicago.edu
(773) 947-0734

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