NEWS: Ichthyosaur fossil in Alaska

tonmo

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Phil

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Re: NEWS: Ichthyosaur fossil in Alaska

tonmo said:
When considering the distribution of prehistoric cephs, it's important to also consider predators and prey.
That the ichthyosaur fed on cephalopods is a certainty. The stomach contents of some species of these ancient marine reptiles have been examined and occasionally show belemnite hooklets. Creatures such as the Jurassic ichthyosaur Ophthalamosaurus appear toothless yet careful analysis of adult specimens have shown that their jaws have very small teeth set in grooves which is the perfect adaption for feeding on squid.

However, it seems likely that most species of ichthyosaur were more opportunistic, feeding on fish, cephalopods and a few have allegedly even demonstrated evidence of cannibalism among juveniles of the same species. (If these animals gathered together to give birth then eating another animal’s young would increase it’s own offspring’s chances of survival). In 1996 a 110 million year old specimen was found in Queensland, Australia, with the remains of a sparrow-sized primitive bird in its stomach (Nanantius eos) along with fragments of turtle shells. This is particularly interesting as it had been a widely held view that the ichthyosaur became extinct due to the disappearance of the belemnites. It seems that some species, at least, had a diverse diet and other factors must have therefore come into play.

This find was discussed here on this thread:

TONMO thread: Ichthyosaurs were Bird Eaters

If anyone is interested in the biology and lifestyle of the ichthyosaur then this is a good site. It has a nice 1850's engraving of a set of belemnite hooklets on the 'Diet' page:

Ichthyosaur Homepage

As an aside, I once read that ammonite shells were composed of calcium carbonate which is easily dissolved in stomach acids. Presumably belemnite hooklets were composed of a much tougher material. Perhaps this explains why ammonite fragments are not found in marine reptile stomachs and that they were not equipped with hooks? (Will try and confirm this, it's been a sometime since I read it).

And lastly, a cuddly ichthyosaur I have at home!
 

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