Re: beaks and teeth

["Jaime A. Headden" <qilongia@yahoo.com>]

Patrick Norton wrote:

<Can anyone provide me a reference for one or more of these finds? For
purposes of an illustration, I'm interested in knowing where on the
jaws(?) the possible rhamphothecal material was found preserved, the
species on which it was found and if the animal(s) were adult or
juvenile.>

  Glut (1983, 1997) have a photograph of an *Edmontosaurus* (labelled
in the first as *Anatosaurus*) with an upper premaxillary rhamphotheca
preserved. The three-dimensional type, not an impression as seen in
some pterosaurs (Wellhofer, 1996?). For those who don't know, the Glut
citations are is _New Dinosaur Dictionary_ and _Dinosaurs: the
Encyclopedia_; _Illustrated Pterosaurus_ for Wellhofer.

<One possible osteological correlate that occurs to me is the location
of the nasal opening in the nasal bone. All extant animals with
rhamphotheca have nasal openings located high up on the beak, and
those openings are directly correlated to the location of the opening
the nasal bone. As I recall, the location of the naris varies widely
among the hadrosaurid species--some located well away from the end of
the snout and others close to the end of the snout. Perhaps the
location of the naris on those animals has some relationship to the
presence or extent of a rhamphothecal covering.>

  Is is the external naris you're talking about? this, actually, has
little to do with the extent of rhamphothecae in birds, and probably
not for hadrosaurids (_en sensu lato_, if Horner's right). Here, the
rhamphothecae with cover much of the external naris in avians, and
only the actual fleshy nares are exposed. In hadrosaurids, there is a
very large fossa around the naris itself, which I've come to call the
narial fossa for lack of a better term. Some theropods had it, most
ornithschians had it. Hadrosaurids flaunt it, or at least
hadrosaurines, and the rhamphotheca in the aforementioned
*Edmontosaurus* clung only to the down-turned margin (or edge) of the
premaxillae. It could have covered more, but the naris may have
extended out into the fossa itself, unlimited by the hole in the
snout. You know, horn-tootin' duckbills like *Saurolophus* where giant
fleshy "sacs" would have increased the nasal chamber. This would have
limited the rhamphothecal coverage considerably, if true.

  My roughly four centavos,

  Jaime
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