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re: Anurognathus dorsal frill



Jaime wrote:

I had not gotten these images from Dave, and did not ask, though I was
curious. (In the future, Dave, could you send these to me,
automatically,
asd I truly do wish to see them? sometimes I am just none to brave.)
However, I have looked at them with the benefit of a friend who sent
them
to me. My own observation of the *Anurognathus* plate Dave prepared to
study for integument was, in fact, that the material he suggests
represents a wing with regular "fibers" along the membrane are easily
just
wing membrane, rather than a dorsal frill. This is problematical, in
that
the skeleton shows the same integument used to suport the frill shape as

being around the foot and along the leg, and within the wing sail,
rather
than external to it. This leads one to doubt this membrane is anything
more than the cheiro, tenio, or cruropatagia. The "fibers" in the
membrane
are in perfect position to be aktinofibrils. Food for thought. Sailfish
sails are bouyed by water, and perform a roll-preventing stabilizing
copntrol, which most flying animals do not need to contend with, dealing

with wings as they do, which do the same thing. Such a structure in a
flying vertebrate is simply not likely, though I do not say they could
NOT
exist. But the absence of a selective pressure for them, when there are
wings, would seem to imply such a thing is less likely to be true than
membrane structures in the wing only.

  I would like to see more thoughts on this.


>>>

It's good to be skeptical, Jaime, but what you saw was a file in which
all the layers were flattened. Don't be confused. It's important to
remember that frills have been observed universally in pterosaurs that
are preserved two-dimensionally and where the matrix has not been
chipped at. It is important to also remember that the narrow chord wing
membrane has been observed universally and without exception in
pterosaurs -- one of the benefits (= curses) of preparing a cladogram.
Thus the broad purple membrane described as the frill is three times
broader than the depth of the wing chord traced in blue. Where they
overlap is a darker blue. The wing cord is of a consistent depth in
Anurognathus and is a _great_ example of this model. In addition there
is symmetry in the wing membranes -- and notably none in the dorsal
frill since it is a parasagittal structure. The purple lines that you
take for actinofibrils are much to widely spaced and, when you look
closely at them, they are quite irregular and often "toothed" with
little scales.

The membrane around the foot is likewise different. It's bumpy at best.

I understand your confusion. I was also confused by those lines
paralleling phalanx 4.1 on the right wing (stage left). They looked like
a series of trailing edge membranes. I often asked myself, Which was the
correct trailing edge? The recognition of the dorsal frill solved that
problem. Those various trailing edges (that actually go all the way to
the sacral region) are simply the divisions within the frill. And the
anteriormost line, the one that is continuous around the wing, is the
true trailing edge.

By the way, I will never send anything automatically. Sorry, you'll have
to request whatever you want. Some people, notably acknowledged
pterosaur experts, do not want unsolicited emails containing new data.
Regretfully, none have requested information on frills, narrow chord
wings, or pregnant pterosaurs.

And now, as of this weekend, I know of a few pterodactyloids that
retained the big fifth toe along with some surprisingly long (= torso
length) tails.

It's a fascinating field.

David Peters
St. Louis