Sauropod nostrils (was RE: joke........)

["Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>]

> -----Original Message-----
> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> carlo godel
>
>However the blood that remained in the head region could have been
> oxygenated by the mere act of breathing since the nostrils were
> placed in such
> proximity to the braincase and the nasal cavities passing
> directly to both sides
> of the braincase there was no need to bring the blood up to the
> brain as it was
> oxygenated from the passage of air over the nasal membranes and
> hence to the
> brain cavity. Just as cocaine does or phenylephrine HCl.
> does. The passage of air over the membranes would act as the pump for the
> circulation, inhale and exhale would apply pressure to the passage. The
> transition from one to the other would release the pressure.
> Hence no need to get
> blood up to the brain against all of that fluid head cause it was
> already there
> and circulation provided for. Why have your nostrils at the top
> of your head if
> not for feeding your brain?

An interesting hypothesis, but please note:
Not all sauropods, or even all long-necked sauropods, have nostrils at the
top of their head.  In _Shunosaurus_, _Omeisaurus_, _Mamenchisaurus_,
_Euhelopus_, and _Camarasaurus_ (to think of a few off the top of my head,
so to speak...) the nostris are still anterior to the orbits and certainly
far less retracted than in (for example) diplodocids or brachiosaurids.

As for other reasons for putting nostrils at the top of your head:
Breathing while most of the body is underwater (okay, does not work for
sauropods, as established long ago, but in vertebrate history this seems to
be the main factor in narial retraction);
Attachment for proboscis: has been suggested for sauropods, but little else
to support this idea;
Attachment for inflatable nose bladder: might work for macronarians, but
unlikely for diplodocids.

And, of course, simply getting the nostrils out of the way of the feeding
area, so the sauropod could be munching leaves without getting twigs in its
nostrils...

                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
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Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
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