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re: Anurognathus dorsal frill



Nick Gardner wrote:

You've mentioned this term several times on list in your posts, so could
you
explain what a "dorsal frill" is?



Nick Gardner
Paleoartist
AIM CloudRaptor05

"And then the cat, the dirty theif, ran away with the dish and the
spoon..."


In Longisquama, it has long been accepted, that a frill of several
extraordinarily long (feather-like) (scale-like) plumes arose from the
dorsal sector of the vertebral series. About three years ago I published
that Longisquama, along with Sharovipteryx, Cosesaurus and other
Prolacertiforms were sister taxa to the Pterosauria. Recent work (as yet
unpublished) describing the posterior of Longisquama, the prepubis of
Sharovipterys, etc. confirms that association.

Knowing that the most primitive known pterosaur MPUM 6009 (currently
referred to as a juvenile Eudimorphodon ranzii (Wild 1978)), and
therefore a sister taxon to Longisquama, also had a lot of "stuff" (=
funny-looking matrix) over its dorsal series, I opened my mind to the
possibility of an overlooked frill and suddenly _there_ it was. Then I
looked at Eudimorphon ranzii and _there_ it was. Then I looked at a
dozen other specimens and every time it appeared. The dorsal frill
actually occupies the cervical, dorsal and sacral series, as in
Longisquama. It appears to be present in Zhejiangopterus and Nyctosaurus
with no reduction in size, so it appears to be universal.

I wrote to a leading expert on pterosaur aerodynamics early on and asked
for his opinion on the subject - how would such a structure affect
flight, etc. Still waiting for an answer on that one. Since it was
totally unexpected and still paradigm-shaking, I don't mind that it
takes some time to arrive at a carefully considered answer. No doubt it
was a display structure. Sailfish may have an analogous structure and
they are among the fastest fish in the sea. I have not seen a pterosaur
dorsal frill that was anything less than completely erect.

Along with the frill comes the observation that nearly all pterosaurs
previously considered to have no crest at all, had a soft crest,
sometimes of enormous proportions, again inherited from the likes of
Longisquama.

The dorsal frill on pterosaurs appears to be a fairly conservative
structure showing only minor changes across taxa. In one case the dorsal
frill is disconnected from the body, but still maintains its connections
internally, so there may be locking mechanisms between frill units in
some specimens. In Jeholopterus the fringy "hair" that was described as
covering the entire torso, actually appears to be fringing the tips of
the frills -- so I'm not sure how "hairy" pterosaurs really were any
more. The ptero-hair on Sordes emanating from the skull is not part of a
frill. It's real ptero-hair.

The easiest frills to see, so far, have appeared on the dark-wing
Rhamphorhynchus and I suspect that the "wing membranes" on BPM 0002
(which may be a derived dorygnathid rather than a pterodactyloid) may be
dorsal frills remains, but its a jumble out there. Otherwise what you
are looking for is a series of joined feather-like shapes, some fringed
with tiny toothy scales, others with ptero-hair.

Baby pterosaurs appear to be born with them.

Frills have been overlooked since 1784, but once you start looking for
them, you can't help but see them. In cases where the matrix has been
cleaned up -- and in cases where 3-dimensional preservation is present
and the matrix has been completely removed -- frills have not been seen,
of course. Maybe we should look for them here as well.

That's about all I know at present.

David Peters
St. Louis