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Dinosaur noses



Greetings, folks,

As promised, another new dinosaur paper before the end of the week.  Since
the online version is up and running, I think it is fine to cite:

Witmer, L.M. 2001.  Nostril position in dinosaurs and other vertebrates and
its significance for nasal function. Science 293: 850-853.

This is part of Witmer & colleagues' longterm DinoNose project.  Larry's
observed that in all but an extremely small number of diapsids the actual
fleshy nostril is located at the anterior end of the external naris (the
opening in the skull itself).  Thus his placement of a (smaller than
previously drawn) nostril at the front end of the naris of T. rex (and in
the paper Triceratops).

Furthermore, as Sedlmayr & Witmer showed at the 1999 SVP meeting, another
clue for the placement of the fleshy nostril is the nasal vestibular
vascular plexus found across diapsids (if not further).   Its position can
be correlated with osteological markers including foramina and grooves.  Now
(here's the cool part) these markers are found *at the front end of the
snout of neosauropods* like Diplodocus, Brachiosaurus, and the like (too bad
the premaxillae of Rapetosaurus aren't preserved).  This supports the idea
that the actual fleshy nostrils of the Big Guys was down at the front of the
snout, and not on the top of the head.  (Note that the DinoNose folk have
not found any evidence yet of a muscular trunk on any neosauropod, or at
least they haven't mentioned such).

With the nostril in this position, this gives a larger narial vestibule in
which air flows in and out (it extends the narial passage outside the bony
skull).  This has implications both for senses (increased surface area for
olfaction) and thermoregulatory physiology (larger surface area for forced
convective heat loss, evaporative cooling, heat exchange, etc.).

As an aside, I noted with some humor that some of the articles about
Rapetosaurus said
"A classic dinosaur gets a new face".  Knowing that Witmer's paper was
coming out the next day, I though "yeah, a REALLY new face!".

Congrats, Larry: extremely cool stuff.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796