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It occurs to me that my current email has a less intuitive setting
system for email, and that some of my last few messages have not been
received by all, so I am going to be sending email in plain text
correctly from now on.



Graydon wrote:


>


  A least gharials are adapted to rapid movements of the snout,
with the structure and elongation of the snout derived to reduce drag
while being swept sideways in the water. It is a distally-oriented
snout, focusing gape and leverage at the rosette instead of more
posteriorly as in *Alligator* or *Crocodilus*. *Gavialis* is, at least,
a primarily aquatic feeder, not neccessarily of fish, but for moving
with quick strikes underwater. This would simply favor piscivory in
diet, but not necessitate it.



  One should, at any rate, separate habitual diet with seeming
adaptations for that diet. One will note that many long-snouted animals
use their snouts for reach or leverage, while many fish-eating animals,
including other fish, tend not to possess long snouts (although for
fish, the gulp adaptation reduces the need for quick-strikes under
water ... few can escape a precision gulper [I know, I know, that
sounds cheesy]).


  Our information therefore tells us only a few things:



  1) Spinosaurid snouts are elongated with a rosette, which maximizes
precision at the tip of the snout instead of along the jaw.


  2) Torsion of the snout is reduced and inhibited through a triangular
cross-section (Rayfield, et al.) while vertical and lateral shear are
not as reduced as in more adapted crocodilians, indicating these snouts
are derived to resist twisting instead of a vertical bite or lateral
play in water.


  3) Dentition is more or less vertical with limited recurvature, while
also possessing often very distinct fluting and limited serrations, if
not so fine as to be a blade, or simply producing a fine carina without
serrations. This morphology is derived to puncture biting, and holding
prey or food items, and not for tearing, indicating a grip-dominating
bite.
 

  4) Fine dentition posterior to the rosette in some (not all)
spinosaurids indicates differentiation of diet between baryonychines
and spinosaurines, with the former possessing larger maxillary
dentition, even though dentary teeth grade into the small rage
posterior to the rosette, while spinosaurines minimize maxillary and
dentary post-rosette dentition, focusing instead on the terminal
rosette.


  5) Acutely pointed, rather than blunted, dentition enforces a diet
that primarily deals with flesh, rather than bone, and thus these
animals were not regular or opportunistic scavengers, although this
could be given that once in a while, a spinosaur would not stop at
tearing up a carcass for whatever choice bits it can get. I would posit
therefore that spinosaurids would be inguinal scavengers when required,
and could not easily process bone.


  Does this help us determine whether or not spinosaurids were
typically piscivorous? I do not think so. They were likely able to eat
fish, just as they would not give up other food items when offered the
opportunity by some unlucky ornithischian or whatever. However, I think
some things can be assumed: Spinosaurids possess jaws that are actually
unlike most living animals today; they cannot be firmly ensconced into
a classic model, despite their similarity to crocodylians, due to
specific features of their jaw and dental anatomy.

Cheers,

  Jaime A. Headden

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


"Human beings, who are almost unique in having the ability to learn
from the experience of others, are also remarkable for their apparent
disinclination to do so." --- Douglas Adams (Last Chance to See)


"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
Backs)


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