Re: forelimb posture

["Allan Edels" <edels@email.msn.com>]

Pat, et al:

    First, you spelled my name correctly; second, the article was
copyrighted 1997 (printed 1998).  The article mentions several reasons why
the sprawl is the most likely stance.  One of the reasons comes from
matching a generic ceratopsian body with a _Ceratopsipes_ trackway.  The
trackway shows a slightly wider stance for the forelimbs versus the
hindlimbs.  The minor sprawl would explain that, as well as the problem with
the elbow bumping into the ribs - which do not show evidence of such damage.
Also there is a (internal) flange on the humerus which would allow the
proximal end to clear the ribcage.

    They based some of their article on Ken Carpenter's mount of
_Chasmosaurus_ at ANSP, in which he attempted to display the animal in an
active, almost galloping pose.  I say attempted, because the animal looks
more like it is dancing than running.

    One of the problems with many dinosaur mounts, is that they confuse the
elongated neck ribs with the true dorsal ribs, and consequently mount the
shoulders too far forward. (I have seen Ken's mount many, many times in the
last 12 years, and I don't think that he made THAT mistake.  However, the
mount is slightly twisted, like the animal is dancing around some
mid-point).

    There are more details, and I won't refer to all of them now (it's 1:45
AM here).  If necessary, I will dig up the additional details.  Suffice it
to say, I think that the case for minor sprawling is good.

        Allan Edels


-----Original Message-----
From: Pat Grant (Library: Serials Catalog <PATG@vax2.concordia.ca>
To: dinosaur@usc.edu <dinosaur@usc.edu>
Date: Thursday, September 24, 1998 9:26 PM
Subject: forelimb posture


>Naturally I left the printout at the office, so can't quote the
>relevant passage, but Allan Edels (sorry if I misspelled that) quoted
>an article by Dodson and Farlow, 1991 (?) in which it was stated that
>the humerus of ceratopsians has to "sprawl" about 30 degrees in order
>to prevent the proximal end of the humerus from bashing into a rib.
>
>This theory is based on a false premise.  The humerus does not
>articulate lateral to any rib; the glenoid is completely free of the
>ribcage, and anterior to it, or as Ken Carpenter put it in a post to
>the DML, Jan. 19, 1996:
>
>"As all naturally articulated dinosaur skeletons show, the first
>dorsal rib bisects the scapula about midway along its length. If the
>Torosaurus were mounted so that the ribcage was narrow at the front
>and wide[r] posteriorly (as in all living vertebrates), and placing
>the scapula so that the first rib bissected it at the mid point, the
>coracoids would be much, much closer (almost touching) and the elbows
>would be brought in."
>
>So, no opportunity for the proximal humerus to bump any rib even if it
>wanted to, and no need to sprawl out the leg to avoid this nonexistent
>problem.  (Carpenter also points out that this misrestoration can be
>caused by mounting the ribs too vertically, which distorts the shape of
>the chest.)
>
>Now, *elbows* bashing into the ribs may be a different matter...
>
>Pat Grant
>patg@vax2.concordia.ca
>