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Ceratopsian Forelimb Articulation



All:

    Sometime in the last few months, someone asked about ceratopsian
forelimbs - Were they fully-errct or did they have a sprawl to them?
Several people (myself, Tracy Ford and others) indicated that there was
slight sprawl to the forelimbs - with the elbows bent out.

    I based my opinion on a particular mount (_Chasmosaurus belli_  at
ANSP), which I knew had been designed to show the ceratopsian as an agile,
fully-erect dinosaur (Ken Carpenter designed and built it).  The forelimbs
show a slight sprawl, as it became evident that without the sprawl, the
_Chasmosaur_ would constantly bang it's elbows into it's ribs (and the bones
don't show evidence of such).  (The humerus has a large inward-directed
flange on the proximal end of it

    Tracy indicated that Protoceratopsian specimens DO allow for the
fully-erect posture in the forelimbs.

    Someone else was disappointed that there was no references to back up
what are merely personal observations.  I have found one:"The Forelimb
Carriage of Ceratopsid Dinosaurs" by Peter Dodson and James Farlow, in
"DinoFest International: Proceedings of a Symposium Held at Arizona State
University" pp.393-398.

    => "....Paul's (1991b) reconstruction of _Triceratops_ shows slight
inward angling of the lower bones of both the foreleg and hindleg.  If there
was more such inward angling of the lower foreleg than the lower hindleg (as
in the American Museum's _Triceratops_ mount - Figure 5), a larger outward
angling of the humerus than 10-20 degrees becomes possible.  In order for
the big internal flange of the proximal end of the humerus to have cleared
the ribcage, we estimate that the humerus would have needed to angle roughly
30 degrees outward from the vertical.
...."

    (Please note that the authors used both skeletal and trackway evidence
to come to their conclusions).

    Hope this helps whoever had any more questions.

        Allan Edels