Pterosaur response from Dave Peters

[Dinogeorge@aol.com]

Dave Peters asked me to post the following response concerning his studies of 
pterosaur relationships to the dinosaur list:

I did not make the mistake of interpreting the skull of Sharovipteryx in
ventral view (tsk, tsk, David, you didn't read the captions). It is the
dorsal view of the palate, merging into the dorsal view of the
premaxilla, broken off from the rest of the skull at its weakest links,
the struts surrounding the nares, orbits and (three on each side)
antorbital fenestrae.  I have yet to see even the crudest line drawing
of any other interpretation. In fact, I'm worried that David has
misinterpreted the AOF situation as the orbit at mid skull, as others
have. If it were the dorsal side of the skull, rather than the palate, I
am wondering why the (nasals?) split in the middle leaving a gaping hole
in the top of the head!  Those are vomers splitting left and right
around the interpterygoid vacuity.

Be that as it may, you can throw the skull away and you still have a
_wonderful_  pterosaur sister taxon. And the same goes for Longisquama,
Cosesaurus, and down the road abit, Langobardisaurus.  (I just knew one
wasn't going to be enough!  Now it appears that four sister taxa are not
enough.)

Simply put, there is no other group of diapsids known that share with
pterosaurs that wonderful elongated first phalanx of the fifth toe.

In addition, in one or more of the taxa you will find the following:

Working up, the metatarsals are subequal in at least one taxon, the
tarsals are identical or advancing toward the pterosaur condition with a
centrale preserved as the medial distal tarsal. The fibula is narrow or
a splint and parrallels the tibia. The tibia is longer than the femur.

The ilium is extended anteriorly, capturing at least four sacrals. The
pubis and ischium are coosified.

The tail is attenuated with hemal arches extending the length of each
centrum. The vertebral count is the same with the last few transformed
through loss of ribs into lumbars. A single head connects all but the
first two dorsal ribs to the transverse processes. The cervicals are
larger than the dorsals and the right number. Narrow ribs extend from
the cervicals , parralleling the centra in the manner of pterosaurs. The
centra are procoelous.

The clavicles overlap. The interclavicle extends anteriorly forming a
keel. The coracoids are taller than wide (not quite struts, but
certainly not ovals). The scapula is extended posteriorly. The sternal
complex is completely pterosaurian in Longiquama. (But why? Who knows!)
A crescentic deltopectoral crest appears in Sharovipteryx. The radius
and ulna are parallel in three taxa. Digit IV is three times longer than
the metacarpal. Digit V is short.

The skull has slit like nares, displaced posteriorly from an elongated
premaxilla. Antorbital fenestra are present in three of the taxa in an
unexpected pattern of three. The posterior process of the jugal is
tipped by a new ossification of the quadratojugal, completely unlike the
pattern in archosaurs, but just like pterosaurs. The orbit is larger
than the AOF and the pattern of skull sutures is just like that in
pterosaurs. The teeth are heterodont, with some taxa displaying multiple
cusps, as in pterosaurs.

If you're looking for something with short wings, Sharovipteryx is your
best bet with a single digit more than six times longer than the (albeit
reduced) ulna. Otherwise all I can say is, "the wings came last," and I
have a paper in review on that subject.

In short, take the tail, the head, the feet, the pectoral girdle, any
part you want, and throw away the rest -- and you still have a better
case for matching pterosaurs to these prolacertiforms than you do to any
archosaur you can name.  And I'll back that up with a steak dinner.

Still having fun, but wish someone out there in academia would come up
with a decent rebuttal,

David Peters