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Amazing Ammonites

12 July 2014

This story is at www.livescience.com/46715-why-ammonites-went-extinct.html … you'd think they would already know as it was about the same time an asteroid struck the Earth – but apparently that is not enough as ammonites were such a successful sea animal and had existed for millions of years. Hence, scientists have pondered the whys and wherefores and come up with an explanation – they were too successful and had adapted to specific niches in the environment. When the asteroid strike caused mayhem in the natural world those niche ecosystems disappeared – and do did the ammonites.

It was all due to long tails, the press release appears to imply. Ammonites were something like squids in tightly whorled shells. The species are related and their diet is/was similar, and involved consuming lots of plankton. It seems that plankton may have been scarce after the asteroid strike. Going by the chalk layers there was a lot of planktonic algae in the Cretaceous – and perhaps this is where it all went.

Nowadays the iconic ammonite adorns many a mantle piece or window sill – and museums all seem to have a specimen. They can also be found in limestone buildings – sometimes the ammonite displayed to catch the eye of passers by. In some parts of the country ammonites occur in fields, often broken by constant ploughing. Small ammonites can be found in Jurassic clays and other geological deposits. There must have been an awful lot of ammonites at one time – or they existed over a very long period of time.

Over the last couple of hundred years lots of ammonites and other fossils of the Jurassic have been found along the so called Jurassic coast of Dorset and eastern Devon, falling out of cliffs (or deposited on the beach by collapsing cliffs). We now have a wonderful online resource where you can look at these fossils on your internet gadget, computer or smart phone or tablet or whatever. Go to http://jurassiccoast.org/fossilfinder

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