Re: Regarding Spinosaurus

["Steve Brusatte" <dinoland@lycos.com>]

On Mon, 7 Jan 2002 19:12:40   
 Graydon wrote:
>> 
>> Interesting idea.  I wish Marco Mendez was still onlist, as I'm sure
>> he would have something to say.  I'll have to e-mail him later.
>> Anyway, I like this idea.  Boy, it would sure throw a kink into
>> Horner's hypotheses (wouldn't it be funny if his big, mean JPIII
>> Spinosaurus turned out to be a scavenger and Tyrannosaurus a predator?
>> :-))
>
>Not a scavenger; a peculiar predator.
>
>(But funny anyway, I think.)

Oh, sure.  I was just being facetious.  I have a really hard time accepting 
that any animal _that_ large could be an obligate scavenger.  

>With large mammals, once you've killed it, getting the guts out of it is
>relatively strightforward; you go in through the stomach area, behind
>the ribs.  With large herbivorous dinosaurs, the ribs go all the way
>back, and that option isn't there.
>
>Tyrannosaurs seem to have got round this by means of very powerful bite,
>capable of crushing bones; there's no reason to suppose that a
>tyranosaur couldn't *bite* through the ribs, or use some combination of
>stand-and-pull to open them.
>
>It seems plausible that different adaptations toward that same basic
>purpose -- get at the guts -- would exist.

Maybe, or perhaps, if your hypothesis is accurate, spinosaurids evolved their 
peculiar jaws, nares, etc. in order to occupy an open niche.  In other words, 
perhaps the more traditional large bodied theropods were not quite adapted for 
extracting the nutritious innards from sauropods and other large herbivorous 
dinosaurs.  It is possible that if your hypothesis holds its weight (it's quite 
hard to test, as HP Williams has commented on), it may explain not only the 
peculiar morphology of the spinosaurids, but how they were able to live 
alongside so many other large predators (see HP Holtz's commentary along Paul 
Sereno et al.'s Science paper on Suchomimus).  

In response to HP Williams' idea that the best way to test this hypothesis is 
to find a "naked" spinosaurid snout: first of all, as he alluded, finding this 
type of integument will likely be very difficult (but with more expeditions to 
Africa, who knows?!).  However, even if it were to be found, a naked 
spinosaurid is not a foolproof way to "prove" Graydon's hypothesis.  Of course, 
there are many other imaginable scenarios that may explain why the snout would 
be naked (even a fish-catching adaptation, such as the use of a naked snout for 
better aerodynamic properties in water, may be feasible).  I still think that 
the best method by which to test this is to compare the spinosaurid skulls and 
dentition to modern forms that perform similar methods of feeding.  Of course, 
as I mentioned earlier, there aren't really any large-bodied animals that may 
be akin to spinosaurids, and the majority of scavengers and hunters that feed 
on the innards of modern animals prey on mammals, whi!
ch!
!
,
 as Graydon mentioned, have a different structural makeup than dinosaurs.  

Short take: interesting idea, difficult to test.

Steve

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