Re: Dinosaur "sails" in today's lizards...

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

----- Original Message -----
From: <Pluto77189@aol.com>
To: <dinosaur@usc.edu>
Sent: Tuesday, August 12, 2003 4:10 PM
Subject: Dinosaur "sails" in today's lizards...


>     I've been reading posts from this list for a couple of years or so, on
and off...  I like that Spinosaurus got publicity from JP3, and I found some
of the discussions interesting, especially when comparing the sail of spino
with other animals, dinosayrs included.
>
>     With spinosaurus, and other sail backed dinosaurs and reptiles, we're
thrown dozens of reasons for the feature.  It's a temperature regulator, a
defenzive threat, blah...blah...   And so many people have said(not
necessarily on this list, I don't think) that the "sail" is not seen in
nature nowadays.  This isn't true.
>
>    Tall dorasl spine s is actually very common in lizards, in South
American Basilisks and sailfin dragons.  They are even more common in
Chameleons--Some of which have EXTREMLY similar sails to Spinosaurus, and
many of which have them nearly identical to the Acrocanthosaurs(I get a good
look at the mounted Acro almost every day.  They have one at the NC mueseam
of natural history, and you can see it from the street.)
>
> I don't have the links "on me" but if anyone's interested,  I can post
some links to some pics of certain Chameleo species that demonstrate the
"sail":
> C.cristatus, C. montium, C. quadricornis, C. Melleri
>
> And some with the "high back" that Acro probably had:
> C. deremensis(I have a breeding group of these)
>
> The "high back" seems to be a camoflage/display tactic, with deremensis,
it helps make them look more like a leaf from the side, but it also makes
them look much bigger(especially in the males)
>
> The "sails" in the other species are(mostly) sexually dimorphic, although
present in the females to a lesser extent, and are used in displays.  They
are there for both attracting mates and scaring off rivals.
>

As someone who has published on the blah...blah... function of dorsal sails,
I would like to suggest that the sails of extant lizards may not be good
analogues for the sails of pelycosaurus and dinosaurs because of the
problems of scaling (sailed pelycosaurs and dinosaurs were much larger than
the sailed lizards), and because no evidence of sexual dimorphism in sail
size in pelycosaurs and dinosaurs has been demonstrated.  Dimorphism in sail
size would be consistent with a display function, whereas sails that are
scaled to body mass (demonstrated in pelycosaurs) are consistent with a
thermoregulatory function.

Chris


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