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Re: Pterosaur beaks



----- Original Message -----
From: "John Conway" <john_conway@mac.com>
To: <dinosaur@usc.edu>
Sent: Wednesday, May 22, 2002 9:46 AM
Subject: Pterosaur beaks


> I have noticed that many pictures of toothless pterosaurs (_Pteranodon_
> etc.) show a small albatross-like hook at the end of the beak. Judging
> from the drawings and photos I have, albatrosses and toothless
> pterosaurs do not have a similar bone structure at the end of the beak.
> Is there any evidence for a hooked beak in toothless pterosaurs?

I cannot think of any evidence that any toothless pterosaurs had a hook at
the tip of the upper jaw as has been illustrated in some life
reconststructions of Pteranodon.  Certainly, there is no evidence of a hook
at the tip in Pteranodon and the structure of the jaw (i.e., essentially
straight taper) is not suited to producing a hooked keratinous beak.  As far
as I know, in those extant birds that have hooked beaks, the upper jaw has a
shape that is curved and suited to growing a hooked beak.  Many other extant
birds have tapering beaks without hooks and that seems to have been the case
in Pteranodon.  I have always thought that the jaws of Pteranodon compared
nicely to those of Maribou storks, but of course Pteranodon had the low
crest extending the upper jaw while the storks have nothing of the kind.

>Are these restorations even plausible?

No.


Some specimens of Rhamphorhynchus from the Solnhofen Limestone preserve
traces (impressions) of  hooked terminal ends of the upper and lower jaws
(see Wellnhofer, P.  1975.  Die Rhamphorhynchoidea (Pterosauria) der
Oberjura-Plattenkalke Süddeutschlands.  Palaeontographica, A 148:1-33,
148:132-186, 149:1-30), which Wellnhofer interpreted as a keratinous beak.
More recently, Frey and Martill described a specimen of Pterodactylus which
clearly had a small hooked keratinous structure at the tip of the upper jaw,
crammed in between the terminal premaxillary teeth (see Frey, E. and D. M.
Martill.  1998.  Soft tissue preservation in a specimen of Pterodactylus
kochi (Wagner) from the Upper Jurassic of Germany.  Neues Jahrbuch für
Geologie und Paläontologie, Abhandlungen, 210:421-441).  Given the clear
evidence of the keratinous hook in Pterodactylus, one can consider what
would happen of the distal end of the jaw grew a keratinous sheath and
realize that it would be hooked just as shown in the fossil; however, we
never would have thought that the animal would have grown the keratinous
sheath if it had abundant premaxillary teeth.

Chris


S. Christopher Bennett, Ph.D.
Assistant Professor of Basic Sciences
College of Chiropractic
University of Bridgeport
Bridgeport, CT  06601-2449