[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Theropod Scapula questions
I've been trying to get my arms around the pectoral girdle, so to speak. In
the process of looking over a lot of shoulders (OK, I'll quit now) there seems
to be a great deal of variability in how they are reconstructed. This isn't
surprising, since there is rarely any bone-to-bone articulation between the
scapula and any portion of the axial skeleton (none in dinos, as far as I
know). However, this does raise a bunch of questions.
1) Quadrupeds are generally reconstructed with the scapulae tucked neatly up
parallel with the vertebral column. However, bipeds, particularly theropods,
are usually reconstructed with the scapulae hanging down at a 45 degree angle.
2) How confident are we on the placement of the Theropod scapula along the
vertebral axis? A few years ago, someone on this list quoted Ken Carpenter as
saying "As all naturally articulated dinosaur skeletons show, the first dorsal
rib bisects the scapula about midway along its length." Is this still the case?
3) What is a "naturally articulated" pectoral girdle, given that there is no
hard connection with the axial skeleton and the possible effects of taphonomic
contraction on the soft tissue connections?
4) In a quadrupedal dino, where and how is the force of impact on the fore-limb
distributed to the axial skeleton? For Maniraptoran bipeds, the hand strike,
flight stroke, or what have you, looks like it would create the opposite
problem. How is this strain distributed to the axial skeleton? It looks as if
the scapula would be the primary agent in both cases, but I don't see how it
interacts with the ribs (or whatever) to do the job.
Thanks for any information you may have.
Vertebrate Notes @