[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Stego/Ankylo limbs



In a message dated 96-02-01 01:50:12 EST, pharrinj@PLU.edu (Nicholas J.
Pharris) writes:

>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.

The huge olecranon process on the ulna, together with the massive crests on
the humerus, virtually compel the forelimb to have had a permanent bend at
the elbow. The forelimb architecture is quite similar to that of the large
Permian therapsids. The question is whether or not the bend was directed
backward or outward. The glenoid is not much help, since it had a
saddle-shaped articulating surface, allowing the arms to move outward as well
as back-and-forth. The big ceratopians could have held their elbows out or
back, probably did both as needed. Ceratopian trackways show the manual
prints pointing outward as well as forward, farther from the center line than
the pedal prints, but not much. Beware the prints reproduced in Bakker's
_Dinosaur Heresies_; I have it on good authority that they're drawn
incorrectly to support Bakker's view of ceratopians as straight-legged. I
don't see how ceratopians could have held their forelimbs _completely_ erect,
but on the other hand I don't see them hunkering down with their
forequarters, either, the way they've often been restored.