Re: Premax. fenestrae / Plateosaurus

["David Krentz" <David.Krentz@disney.com>]

Reply to:RE>>Premax. fenestrae / Plateosaurus                10:36 AM   
9/8/99

  If  there were air sacs in the antorbital fenestrae, would they expand and 
contract when the creature ex/inhaled or opened and closed it's mouth? If 
they did, would that be noticed on the creatures face in life?  
  David Krentz
Walt Disney Feature Animation
--------------------------------------
Date: 9/8/99 6:18 AM
To: David Krentz
From: tholtz@geol.umd.edu
> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Martin Baeker
> Dear dino-experts,
>
> I sent these two questions a while ago, but nobody sent an answer. So here
> I go again.
>
> 1. Is the function of the antorbital fenestrae (I hope that is the right
> term for the "holes" in front of the orbit in dinosaur skulls) known?

That is the correct name for the structure.  As for the function: Larry
Witmer devoted his doctoral studies to that subject, the results of which
were published as:

Witmer, L.M.  1997.  The evolution of the antorbital cavity of archosaurs: a
study in soft-tissue reconstruction in the fossil record with an analysis of
the function of pneumaticity.  Society of Vertebrate Paleontology Memoir 3.
73 pp.

He was able to reject two previous hypotheses for the function of the
fenestra: housing a salt gland and a site for jaw muscle attachment.  He
supported an association between the fenestra and the paranasal air sinus.
>From the abstract:
"The second step in discovering the evolutionary significance of the
antorbital cavity is to assess the function of the enclosed paranasal air
sac.  In fact, the function of all pneumaticity is investigated here.
Rather than the enclosed volume of air (i.e., the empty space) being
functionally important, better explanations result by focusing on the
pneumatic epithelial diverticulum itself.  It is proposed here that the
function of the epithelial air sac is simply to pneumatize bone in an
opportunistic manner within the constraints of a particular biomechanical
loading regime.  Trends in facial evolution in three clades of archosaurs
(crocodylomorphs, ornithopod dinosaurs, and theropod dinosaurs) were
examined in light of this new perspective.  Crocodylomorphs and ornithopods
both show trends for reduction and enclosure of the antorbital cavity (but
for different reasons), whereas theropods show a trend for relatively poorly
constrained expansion.  These findings are consistent with the view of air
sacs as opportunistic pneumatizing machines, with weight reduction and
design optimality as secondary effects".

I will defer on the _Plateosaurus_ question to those who know more of the
details of prosauropod anatomy than I.


                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.inform.umd.edu/SCHOLAR/programs/elt.html
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796