RE: Longisquama reconstruction sensu Headden

[Jaime Headden <qi_leong@hotmail.com>]

  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.

  Cheers,

Jaime A. Headden

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

"Human beings, who are almost unique in having the ability to learn from the 
experience of others, are also remarkable for their apparent disinclination to 
do so." --- Douglas Adams (Last Chance to See)

"Ever since man first left his cave and met a stranger with a different 
language and a new way of looking at things, the human race has had a dream: to 
kill him, so we don't have to learn his language or his new way of looking at 
things." --- Zapp Brannigan (Beast With a Billion Backs)

_________________________________________________________________
Windows Live™: Keep your life in sync.
http://windowslive.com/explore?ocid=TXT_TAGLM_WL_allup_1a_explore_042009