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Re: Marine question



 --- David Marjanovic <david.marjanovic@gmx.at> wrote:


they [ichthyosaurs] disappeared at the
> Cenomanian-Turonian boundary... which is
> associated with a terrific Oceanic Anoxic Event and
> a considerable mass
> extinction.

There was an earlier major ichthyosaur extinction at
the Jurassic-Cretaceous boundary. Here all the
opthalmosaurids, along with cryptocleidid plesiosaurs
simultaneously disappear. Only generalist predators
(including the platypterygians) and predators of large
prey survived this event. The ichthyosaur's role in
the ecosystem was subsequently refilled by a radiation
of short necked plesiosaurs with heads and teeth
strikingly similar to those of the ichthyosaurs.
However, the ichthyosaurs were not out competed.
Whether the cause of this event has been pinned down I
am not sure, but it is interesting that it coincides
with dinosaur extinctions on the terrestrial
environment.

Adam
Bristol



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