Paleobiological implications of dinosaurian hyoids

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

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Steve Brusatte
>
> I have come to the opinion that dinosaurian hyoids are most
> certainly understudied (although, as Wanger said, they may be
> more common than the literature makes it seem).

Actually, it is even broader than you suggest.  VERTEBRATE hyoids are
understudied, not merely those on that particularly lovely branch of Amniota
we call Dinosauria.

> However, when
> present these bones can give insights into the vocalization
> abilities of dinosaurs, along with information on the dinosaurian
> tongue (which can further be used to possibly deduce feeding
> habits, muscle mass, etc.).  Not to pry, but is anyone currently
> doing any work on dinosaurian hyoids?  If not, and even if so, I
> would be most interested to possibly begin looking closer at them
> next year when I finally have access to a college library.

There is some excedingly excellent work being done on one aspect of modern
animal hyoids: Elizabeth Brainerd's studies of amniote breathing.  Here's
the abstract from SVP 2001:
http://www.bio.umass.edu/biology/brainerd/svp/abstract.html

and here's the website with plenty of videos of different forms of
hyobranchial behaviors.

In brief, a summary:
Everything you know about breathing is wrong.  (Okay, a little overboard
there, but bear with me).  Mammalian breathing is damned peculiar compared
to the system used by other groups of vertebrates.  For example, we need to
use our lungs and diaphragm to sniff and to pant; this is not true for
reptiles.

Dr. Brainerd has demonstrated a series of various behaviors found in the
diapsids and in amphibians.  These include buccal pumping ("swallowing" air:
the way that air-breathing fish and amphibians inflate their lungs), buccal
oscillation (closing the mouth and using the hyobrachial apparatus to pump
air into and out of the mouth, and thus probably smelling the air: in other
words, sniffing without breathing), gular fluttering (leaving the mouth open
while pumping the hyobrachial apparatus, and thereby probably dumping excess
heat: in other words, panting without breathing), and gular pumping (a
derived rather than a primitive form of "swallowing air" used by some living
lizards).

The work on living taxa alone is complex, but has broad implications for the
evolution and diversity of olfaction, heat regulation, and above all
respiration.  Thus, it is somewhat of a mammalian bias (understandable,
since that system is the best studied) to assume that hyoid adaptations =
tongue adapations.

Cool stuff.  The next time I was at the zoo after SVP 2001 I watched their
alligator, and it indeed did a bit of buccal oscillation in between
breathing.

                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