Re: "Acro" ribcage dilemma

["James Norton" <JNorton@une.edu>]

Most theropod rib cages seem narrow, since the trunks of these creatures
are laterally compressed compressed to some other animals.  But the
angles of the rib articulations with the dorsal vertebrae, the rib
curvatures, and the attachments of the anterior ribs with the sternum
all combine to produce reasonably large change in volume with small rib
movements.  My Deinonychus rib cage computer model studies have shown
that this laterally-compressed therod can produce changes in tidal
volume comparable to those of mammals or birds of similar body mass,
with physiologically appropriate degrees of shortening in the
ventilatory musculature.  Whether a sudden dash after a prey is
completely anaerobic or not we'll never know for these creatures, but
they seem to have rib cages that can support aerobic levels of
ventilation for sustained aerobic activities.

JMN


>>> "Jordan Mallon" <j_mallon@hotmail.com> 04/16/2001 10:57:29 a.m.
>>>
G'day all,

Just got through watching a taped episode of "Dinosaur Attack" last
night, 
featuring Dr. James Farlow and sculptor Dave Thomas (God rest his
soul), and 
something puzzled me.  In the show, Dale Russell suggests something to
the 
effect that because the ribcage of _Acrocanthosaurus_ was so narrow,
the 
animal would have relied solely on an anaerobic metabolism when chasing
prey 
since it would not have had the capacity to inhale much air in times 
strenuous activity.  That said, that's about all that the explanation
the 
viewer got, and so I was just wondering if anyone might be able to
elaborate 
on this for me.  Were there any other theropods that might have
exhibited 
this adaptation?  So far as I know, we all shift gear to anaerobic 
respiration in times of physical stress, but not to the same extent as

Russell seemingly proposed for _Acrocanthosaurus_.
Thanks in advance.

-Jordan Mallon

http://www.geocities.com/paleoportfolio/ 


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