Re: Spinosaurs as what?

[Renato Santos <dracontes@hotmail.com>]

Tim Williams wrote:

> Before you go too much further with this, I would caution that not 
> everybody is so keen on the idea that spinosaurids spent most of their time 
> in water catching fish.

And I want to scare those persons up so they can have a say on my 
meanderings. And thanks for the info and references :-)

> Sues et al. (2002) point out that the long narrow snouts of spinosaurids 
> and piscivorous crocodilians (e.g., gavials) are actually rather different. 
>  Spinosaurids have flat-sided snouts that are convex on top, whereas the 
> snouts of fish-eating crocs are more tubular.

Much like any Ciconiidae (flightedness nonwithstanding) and storks don't 
only eat fish ;-) ( http://en.wikipedia.org/wiki/Stork ).

>  Sues et al. (2002) suggest that this morphology, like the extensive 
> secondary palate, rendered the spinosaurid snout less susceptible to 
> bending stresses, and was not a piscivorous adaptation per se.  They also 
> suggest that the shape of spinosaurid teeth (conical or only weakly 
> recurved) are "consistent with their use for impaling and holding prey".  
> All in all, they suggest that the jaws of spinosaurids were adapted for 
> seizing small prey.  The authors conclude:

Interesting... _Lepidotes_, the fish found with _Baryonyx_ had what size 
range?

> [snip] Most likely spinosaurid theropods rapidly and forcefully seized 
> smaller prey, which was then processed by dorsoventral motion of the head 
> facilitated by the powerful neck musculature. [snip] Previous anatomical 
> comparisons between the feeding apparatus of crocodylians and spinosaurid 
> theropods were based only on superficial resemblances.
> The postcranial skeleton of _Baryonyx_ lacks any obvious specializations 
> suggestive of an aquatic or semiaquatic mode of life (Charig and Milner, 
> 1997).

My thoughts exactly! But I do like playing devil's advocate, if the list 
members don't mind, that is. But still what function had their big thumb 
claws? Are they just a result of the scaling up their bodies suffered while 
evolving? Are they display devices or means for some not yet forseen 
function?

> Also, don't forget that there is evidence that pterosaurs were also part of 
> the spinosaurid diet.  The remains of one pterosaur were found with a 
> spinosaurid tooth embedded in its neck vertebra.

Yes, and I think the only way the tooth could have gotten wedged there would 
be if the spinosaurid was specifically trying to capture the pterosaur. 
Whether it was predation or just eliminating a nuisance is open to 
discussion...

Renato Santos

P.S.: If you don't mind I'd rather reply to the list than to have two or 
more emails with the same content if I reply to each person individually.

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