Christiansen and Bonde, 2002 (was Re: Feduccia Reviews Paul's DOTA, Comments)

["Tim Williams" <twilliams_alpha@hotmail.com>]

Mickey Mortimer wrote:

> Actually, a paper was written for the exact purpose of refutting Jones et 
> al.'s arguments-
> Christiansen and Bonde, 2002. Limb proportions and avian terrestrial 
> locomotion. J. Ornithol., 143, pg. 356-371. Not without its problems, but a 
> good study nonetheless.

I was very impressed by the paper.  Centre of mass (CM) calculations are 
always a little "warm and fuzzy" when it comes to fossil taxa.  They involve 
a LOT of assumptions - lung volume and extent of pneumaticization; width at 
the chest and hips, etc.

However, IMHO the most sigificant finding of Christiansen and Bonde (2002)'s 
study is that the femur of _Caudipteryx_ appears to no show thickening of 
the diaphysis associated with avian locomotion patterns (contra Jones et 
al.).  Modern birds have proportionally shorter and thicker femora, because 
of their derived hindlimb kinematics (rotation occurring about the knee 
rather than the hip, which puts greater stress on the femur, which is 
oriented subhorizontally during non-rapid terrestrial locomotion).  The 
circumference of the femur in _Caudipteryx_ is significantly less than that 
of ground birds, and similar to other non-avian theropods.  I think this 
result deals a lethal blow to the idea that _Caudipteryx_ was a "Mesozoic 
kiwi" that had an avian-style posture.  _Caudipteryx_ was a long-legged, 
short-tailed non-avian theropod.




Tim

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