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Re: Spinosaurs as what?



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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