RE: Pelicosaurs: sprawling or not?

["Tracy L. Ford" <dino.hunter@cox.net>]

-----Original Message-----
From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
Steve Brusatte
Sent: Tuesday, April 16, 2002 2:16 PM
To: dinosaur@usc.edu
Subject: Re: Pelicosaurs: sprawling or not?

On Tue, 16 Apr 2002 11:39:37
 David Marjanovic wrote:
>> I was under the impression that even monotremes have a semi-sprawling
>posture and that, among
>> synapsids, fully erect stance is seen only in therians. Would like to
know
>if this is wrong.
>

I've read Tracy's article (published in the October/November 2001 issue of
Prehistoric Times). He offers two lines of support for a "more erect gait
and not the more typical illustrated sprawling one" in pelycosaurs:
footprint evidence and the position/size of the olecranon.  Others on the
list are probably better off to answer what significance the olecranon has.
However, I do know the footprint evidence upon which Tracy based his
hypothesis are some trackways of _Dimetropodus_, which show the prints
closely placed next to one another.  I haven't seen the tracks myself, but,
just to keep it "real:" obviously, we don't know if _Dimetrodon_ or any
other pelycosaur actually made the _Dimetropodus_ tracks.

Of course, there is also the possibility that some pelycosaurs could have
evolved a more erect gait independent of the lineage that lead directly to
mammals.  I doubt there is enough evidence to test this yet, though.

Tracy's hypothesis is interesting.  Hopefully we can illuminate it with new
fossil material in the future!<<

Steve

Thanks. I based my hypothesis on the neural spines and how they may have
held the back stiffer than people think and from Hunt & Lucas, 1998

Hunt, A. P., and Lucas S. G., 1998, Vertebrate tracks and the myth of the
belly-dragging, tail-dragging tetrapods of the Late Paleozoic: In: Permian
Stratigraphy and Paleontology of the Robledo Mountains, New Mexico, edited
by Lucas S. G., Estep J. W., and Hoffer J. M., New Mexico Museum of Natural
History and Sciences, Bulletin n. 12, p. 67-69.

And they are the ones who have identified the Dimetropodus (or at least
agree with others who have identified them as belonging to pelycosaurs) and
these tracks have a narrow gait.

This also reminds me I'm suppose to send someone a copy of this article. I
too hope that in the future more will be written up on this subject.

Tracy L. Ford
P. O. Box 1171
Poway Ca  92074