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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 metre) across—possible snack food for the giant mosasaur Tylosaurus.
Ammonites constantly built new shell as they grew, but only lived in the outer chamber. They scooted through the warm, shallow seas by squirting jets of water from their bodies. A thin, tubelike structure called a siphuncle reached into the interior chambers to pump and siphon air and helped them move through the water.
Size: Some more than 3 ft (1 m) in diameter
Group name: School
Did you know? Female ammonites grew up to 400 percent larger than males, presumably to make room to lay eggs.
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