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Re: Spinosaurid Nose Job



George Olshevsky (Dinogeorge@aol.com) wrote:

<Just out of curiosity, why move the narial openings up to the top of
the skull if you're going to leave the external nares at the front of
the skull? This apparently happened independently twice in sauropods
(diplodocids and titanosaurs).>

  As I see it, it increases the nasal passage and vascular surface
with a conservancy of bone. Different approaches may have been
secondary adaptations to feeding behavior, and the elongated plan may
have occured twice while the narial position is unique among groups
(even nemegtosaurs from diplodocoids). The broken rostral process of
the nasals in *Nemegtosaurus* suggest to me that a intranarial bar
was present, but not in *Rapetosaurus* or the nemegtosaurid-like
skull of *Antarctosaurus wichmannianus* (do not confused with the
mandible :)). The nasal arch of *Brachiosaurus* is rather slender,
and retracted from the dorsal basin on the snout, indicating a good
deal of possible cartilage or soft tissue extension, even an
inflatable nasal vestibule. Less so for the camarasaur-*Jobaria*
skull type, as in *Malawisaurus*, where the intranarial bar is much
broader, and the nares would be in the anterior position....

  What Witmer has done for a few needs to now be compared to
individual taxa on the basis of certain criteria he details, rather
than applying the anterior position generally. I actually reconstruct
diplodocid snouts with a large cartilagenous hump over the bony
nostrils, then extend these to the rostral fossa for the nares in
vestibulae. The result is a superficially "bulky" skull.

=====
Jaime A. Headden

  Aaaaaaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhr-gen-ti-na
  Where the Wind Comes Sweeping Down the Pampas!!!!

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