Longisquama reconstruction sensu Headden

[David Peters <davidpeters@att.net>]

With the Headden reconstruction of Longisquama in front of me, the following 
comments come to mind.

Excellent proportions and technique.

Not sure why a bipedal stance was not chosen given the limb length disparity 
and erect carriage shown here. It seems as though it is straining to get into a 
quadrupedal configuration.

Note the posteriorly displaced naris, as in basal pteros (anuros rotate this 
vertically reducing the displacement). Good.

Antorbital fenestra is controversial. I agree there was one. I think, however, 
that it was reinvaded by dorsal processes of the maxilla, dividing its aperture 
and causing confusion (i.e. There? Not there?)

I think there is a large nasal, frontal crest that I don't see here. Perhaps 
Jaime has rotated these elements into the horizontal plane as would be common 
among tetrapods. And maybe that is correct. 

The occiput and palate in the holotype have rotated into the parasagittal plane 
and these are not indicated here. But then, it's a lateral view.

 Along the same lines, the ascending process of the premaxilla is also 
displaced and lying across the lateral rostrum in the holotype. Replacement to 
its natural position shows that it extended as far as the orbit and slightly 
raised the nasal crest, if present as a crest.

The quadrate area seems very unreptile like. Is that a squamosal below the 
postorbital? If so, this may have resulted from confusion with the rotated 
occiput. The squamosal would lengthen the postorbital portion of the skull if 
replaced to its standard position. The quadrate should extend to the upper rim 
of the lateral temporal fenestra. The anterior extension of the quadrate may be 
the other quadrate displaced. Not sure. The jugal and quadratojugal are very 
fenestrasaurian. Good.

The teeth are much too simplified in the recon. Many should be multicusped and 
most contact their neighbor, as in basal pteros.

The first five cervicals should be shorter than the final three, but the 
Headden reconstruction is very close. 

I would rotate the ventral ribs further posteriorly, as is common in tetrapods. 

The scapula is spot on. The clavicles, partly obscured here, should be tornado 
shaped, gracile below, robust above, but the size is right here.

I'm guessing the famous 'furcula' of Longisquama is here seen in edge-on view. 
That would be true if related to anything but Cosesaurus and pterosaurs in 
which the clavicles rim the sternum. I don't see the interclavicle extending 
beyond this clavicular rim in the Headden reconstruction, as Sharov and I 
traced it. A ventral view of the sternal complex would help here.

The humerus looks good, although as I recall the deltopectoral crest is more 
pronounced in the holotype. Might be dislocated from the glenoid in that 
position. Further back will put it more in the cup.

The antebrachium should have both elements in close sliding contact, not 
separated by whatchacallit, that interosseous space. 

The carpal elements will bunch closer together when the ulna and radius regain 
contact. Some unindicated surprises will also appear in the carpus once all the 
elements are properly identified.

The neutral pronation/suppination of the hand is perfect. As in pteros. Let 
fingers I-III touch the ground, if quadrupedal.

The metacarpals are good, but metacarpal IV should be somewhat wider than three 
and distally rotated into the plane of the hand. Note the proportions of the 
metacarpals are quite similar to those of Cosesaurus and basal pteros. And good 
to see metacarpal V there.

I see in the reconstruction the post-humerus soft tissue Jaime referred to 
earlier. That is correct. Expect more soft tissue to spread further posteriorly 
following the antebrachium and fingers, as I speculated in Peters 20002.

David Peters
davidpeters@att.net