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Identify a specimen... Ammonite Ammonoidea

Ammonites first appeared in the sea about 380 MYA and became extinct at the same time as the dinosaurs, 65 MYA. They are famous for their distinct, chalky spiral shells, which end in an opening from which the inhabitant's head protruded.
 
Inside the shell lived a squid, probably with short tentacles similar to those of the nautilus, a distant modern relative. Ammonites moved by ejecting water through little tubes called hyponomes, which meant that to an observer they would have appeared to be moving backwards. Their large round eyes were set under a hood.

Ammonites were preyed upon by marine reptiles and other large sea-dwellers. For this reason, they evolved a number of defensive features, including the shell, the hood and possibly the ability to squirt watery black ink at attackers' eyes to make themselves temporarily invisible.

See also: belemnites

 

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