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Varanid noses (was RE: Did We Get Dinosaurs' Noses Wrong? OPINION (Stanford))



> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Michael Bruce Habib
>
> An interesting point came to mind when you mentioned the
> Komodo dragon, as some other species within Varanus have
> nostrils further back.  Basically, within this genus, you
> find nostrils at a number of different positions, but all
> monitors are carnivorous.  So, while the nostrils have
> about the same position in all cats and dogs, we can see
> some variation in the monitors, despite the fact they are
> all predators.  That being the case, I would tend to doubt
> that carnivory determines nostril placement, or selects for
> nostrils of different locations.  Other factors, such as
> semi-aquatic behavior, or burrowing, etc. seem to be more
> important.

Actually, varanids are one of the particular exceptions Witmer addresses (p.
852, and also note 6).  He points out that _V. griseus_, _V. dumerili_, _V.
exanthematicus_, and others (not _V. komodoensis_ or _V. giganteus_, though)
have fleshy nostrils in the middle or rear half of the external nares.
these same lizards have apomorphically enlarged vomeronasal organs (not
"vameronosal organs", as I was about to type...) which (also apomorphically
among diapsids) lies anterior to the fleshy nostril.  Thus the position of
the nostrils of these lizards seems to have to do with their specialized
VNO, and not their diet.

                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