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In all known quadrupedal dinosaur trackways the hindfeet nearly touch the
midline or are separated by no more than one foot width. The handprints are
often but not always a little further from the midline, being separated by
one to two handprint widths.
The very large trackways very probably correctly attributed to Triceratops
(the only viable four toed alternative being a giant nodosaur so far not
known from that time and place) has the touching the midline, so the legs
sloped down and in from the hips, with the knee bowed out a little like in
rhinos. The hand prints are somewhat further out being separated by two
handprints, which places them immediately below the shoulder joints. The
elbows probably were bowed out a little, which is true of rhinos and other
ungulates. The substantial projection medial to the humerus head, which was
also present in sauropods, would not have interfered with the ribs because
the shoulder joint was located forward of the anterior ribs. There is no
evidence that the arms were semi-sprawling during normal locomtion, although
they may have been able to assume such a posture when drinking or during slow
speed combat. This is detailed in the 2000 paper I co-authored with Per
Christiansen in Paleobiology 26:450.
The new Smithsonian mount has the hindfeet separated by about three or four
foot widthes, causing the legs to splay out in a manner not compatible with
any dinosaur trackway. The hands are separated by three or four hand widths,
also much greater than observed. Some of the joints do not appear to be fully
articulated. There are problems with the configuration of the scapular
glenoid, which is often distorted by crushing but faces partly inwards in 3-D
preserved examples of Triceratops and other ceratopsians large and small. I
do not believe any of the well preserved glenoids were digitized.
If moi ever gets a chance to design a Triceratops mount I'll plop the sucker
directly onto the trackway, with any size differences accounted for. Should
be the standard procedure in my humble opinion.