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TOPIC: Ammonites


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RE: Ammonites
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Ammonites are an extinct group of cephalopod molluscs related to the modern chambered nautilus, squid and octopus. Although it had an external shell like the chambered nautilus, it appears to be more closely related to the cephalopods that lost this feature. The basic structure of nautilus and ammonite shells are the same, except for the notable difference of the septa separating the various chambers. In the nautilus it the septa simply forms a smooth curve, while in ammonites they developed into increasingly complex patterns of folds and wrinkles (referred to more formally as peaks and saddles) over the course of their evolution.

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Before the Rocky Mountains rose to touch the sky, a vast inland sea stretching from the Arctic to the Gulf of Mexico covered much of North America, including what would become Colorados Grand County. And in that primeval sea lived a species of odd-looking creatures that were half-giant snail and half-squid that scientists now call ammonites.
The ammonites were marine predators that hunted, reproduced, died and eventually became extinct 72 million years ago in that long-ago sea. The only thing that remains of them today is their fossilised bodies.

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Ammonites were predatory, squidlike creatures that lived inside coil-shaped shells. Like other cephalopods, ammonites had sharp, beaklike jaws inside a ring of tentacles that extended from their shells to snare prey such as small fish and crustaceans. Some ammonites grew more than three feet (one meter) acrosspossible snack food for the giant mosasaur Tylosaurus.

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Perisphinctes ammonite species from the Tulear region from the  island of Madagascar
This unique invertebrate was part of marine life over  160 million years ago.
Ammonites are extinct members of the Cephalopod class.  Modern members include nautilus, squid and octopus.  They first appeared during the Silurian Period (435 million to 410 million years ago) and were abundant and widespread in the seas of the Jurassic and Cretaceous periods (175 million to 65 million years ago).

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