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Re: Stego/Ankylo limbs



On Thu, 1 Feb 1996, Van and Kathy Smith wrote:

At 03:03 PM 1/30/96 -0500, Dinogeorge@aol.com wrote:

>Since ceratopians were secondarily quadrupedal (the ancestral ceratopians
>were small bipedal marginocephalians and psittacosaurs), there is no reason
>to expect their graviportal forelimbs to have had a pose as fully erect as
>their hind limbs, which had been primitively erect (a dinosaurian apomorphy)
>for about 150 million years. Indeed, because the large, graviportal
>ceratopians had evolved quite rapidly during essentially the second half of
>the Late Cretaceous (about 20 million years altogether), one would not expect
>much in the way of a fully erect pose--the result of lengthy evolution--from
>the formerly grasping forelimbs. The forelimbs became suborned in a "fast and
>dirty" way to holding up the animals' forequarters, letting the "evolutionary
>chips" fall where they may. Perhaps, had there been no terminal Cretaceous
>extinction event, the forelimbs of ceratopians would eventually have trended
>toward a more fully erect pose, but now we'll never know.

George, I'm surprised at you!  As I mentioned in a previous post 
(although I'm not sure it ever left campus, thanks to this @#$$%^$%@ 
e-mail system), EVEN BIPEDAL ORNITHISCHIANS HAVE ARMS MOUNTED ON THE 
UNDERSIDES OF THEIR BODIES!  At any rate, there were actually probably 
very few obligate bipeds among the Ornithischia.  _Iguanodon_ and 
_Psittacosaurus_ did not sprawl when they went down on all fours, and 
neither did neoceratopians.

Nick Pharris
Pacific Lutheran University
Tacoma, WA 98447
(206)535-8204
PharriNJ@PLU.edu

"If you can't convince them, confuse them." -- Harry S. Truman