Cameroceras was a giant orthocone nautiloid that stalked the shallow seas of the Ordovician period, around 470 million years ago. It was one of the largest animals of its time, with a long, straight, cone-shaped shell that could reach several meters in length, made of many sealed chambers that it filled with gas to control its buoyancy. From the open end of that shell emerged a muscular body with a ring of grasping tentacles, which it used to seize fish and trilobites before dragging them to its beak-like mouth. Cameroceras was an ambush hunter, jetting backward through the water by forcing water out of its mantle, and its fossils are found in shale deposits worldwide. Its DNA can only be recovered from shale fossils.