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RE: Longisquama reconstruction sensu Headden
Do understand that the reconstruction is not only years old, but that I made
a specific point of restoring it into a quadrupedal posture. It is unlikely in
my opinion, based on the specific quality of the shoulder girdle and the
proposed systematic position and therefore close taxa, that this animal wasn't
sprawling. However, that being said, many of the limb elements imply a
straighter limb posture than many lizards would have, and this animal was
likely less sprawling than even crocodilians. But that's as far as I would go.
I measured all bones from a single photograph and from given scales from
multiple papers to cross-reference, as well as the original Sharov work (which
I no longer have a copy of), so any mis-estimates are both mine and in the
sources, as a result of insecurity in determining elements in the photographs.
Now for some specific criticism:
The entire snout region is not to be trusted. There is a projection of a
large naris, long and simple nasal, and shallow and simple maxilla, without
much of a complex rostral anatomy. This is, in my opinion, an illusion fostered
by the crushing of the skull. I reconstructed the skull largely in light of an
ornithodiran ancestry, and therefore that the antorbital fenestra was a given;
each of the apparent bone margins would have had to fit that model to enforce
the idea, even though as I noted in my previous post that I thought this was
subjective. It is. We would tend to view such indistinct features in light of
our hypotheses in order to favor them. I was trying to restore the idea of an
ornithodiran without advocating it.
Unfortunately, here, the skull dorsal margin and occipital position are
beyond the point of simple displacement, as they have been specifically rotated
to their sides (as a flattened trapezoid collapses into a single plane), and as
such, the occiput is no longer authentic in its position, rotation, etc. I
tried to fit it to the lateral bones, and projected nothing unique to these
bones to favor the occiput, so it is as rotated as the element on the slab is.
I will cry foul on this one. There is no evidence, nor photograph fine enough
that I've ever seen, to determine a multicuspidate condition in such a way that
anyone has described it. This is literally putting the cart before the horse --
since most of the taxa you associate it with have multicuspidate teeth,
therefore this taxon should? There is no reason to suspect multicuspidate
teeth, and it should not impact its phylogenetic position were it to develop
monocuspidate ot ziphodont denition as an apomorphy in light of whether its a
lepidosauromorph, pterosauromorph, or dinosauromorph, or even a crocodilomorph.
Jaime A. Headden
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