Re: pterosaur nostrils

["Chris Bennett" <cbennett@bridgeport.edu>]

----- Original Message -----
From: Thomas R. Holtz, Jr. <tholtz@geol.umd.edu>
To: <dbensen@gotnet.net>; <dinosaur@usc.edu>
Cc: <Mickey_Mortimer111@msn.com>
Sent: Tuesday, August 13, 2002 5:16 PM
Subject: RE: pterosaur nostrils


> > From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> > Daniel Bensen
> >
> > Where are they?  Pterosaur nares can be really big (in the large,
> > later forms, specifically), and of course the actual holes
> > through the skin can't be that big.  So where were the nostrils
> > likely to be?  Toward the front?  The back?  The top? What's most
likely?
>
> Well, for one thing, the "nares" of later pterosaurs probably is an
amalgam
> of the nares proper and the antorbital/preorbital fenestra.  Thus the
caudal
> part of this opening probably housed the pneumatic tissues presumably
> present in the antorbital fenestra.
>


The bony naris of rhamphorhynchoid (=non-pterodactyloid pterosaurs for those
of you who faint at the sight of a paraphyletic group) is large, but not
particularly so; however, the statement in the original question that the
naris may be large in later forms suggests that the question pertained to
the pterodactyloid pterosaurs.  Tom Holtz is quite correct to note that the
single large opening in front of the orbit in pterodactyloid pterosaurs is a
confluent naris and antorbital fenestra; however, I cannot agree with the
unstated implication of his statement to the effect that the caudal part of
the confluent naris and antorbital fenestra housed the tissues associated
with the antorbital fenestra. The implication of this is that the anterior
part housed the naris.

Rhamphorhynchids [how much do you want to bet the Rhamphorhynchidae is
paraphyletic, too?] are generally viewed as the closest sister group of the
pterodactyloids, and the arrangement of the naris and AOF in the Chinese
rhyamphorhynchid Angustinaripterus may show a stage close to the fusion of
the naris and AOF.  In Angustinaripterus the naris is longer and more
slender than in other rhamphorhynchids and extends quite far posteriorly
OVER the AOF.  If one assumes that this condition represents essentially the
last step before the fusion of the two openings, then after fusion it would
be likely that the narial part of the confluent naris and antorbital
fenestra would be at the top and posterodorsal corner of teh opening.  THis
interpretation might be supported by the fact that the nasal bones are
displaced posteriorly in pterodactyloids such that they are over the
posterodorsal part of teh confluent opening.  In addition, the nasals send a
median process ventrally into the confluent opening.  Peter Wellnhofer was
of the opinion that the nasal process were not median, but rather were on
the lateral surface of the skull and that they represented a remnant of the
bony separation of the confluent naris and antorbital fenestra.  That view
is incorrect--the nasal process is median and cannot represent a remnant of
the bony separation of the openings, but it might be associated with the
nasal septum separating the two nasal passages (just because the right and
left openings may be confluent in birds, does not mean that that was hte
case in pterosaurs).  So, pterodactyloids seem to have followed a trend
begun in rhamphorhynchoids to move the external naris posteriorly and
dorsally.  In a visual predator that regularly sticks its jaws in the water,
there would be no disadvantage in moving the naris posteriorly away from
food items and there might be advantage in getting the naris back so that it
was not always dunked under the water.  Despite the very large opening in
the skull, I suspect that the soft tissue opening was up and back, and that
is why I illustrated it so in the life reconstruction of Germanodactylus
that was on the cover of JVP recently.

I hope this helps!

Sincerely,

Chris


S. Christopher Bennett, Ph.D.
Assistant Professor of Basic Sciences
College of Chiropractic
University of Bridgeport
Bridgeport, CT 06601