Helicoprion, whorl-tooth shark Dimorphodon This giant Isotelus trilobite is

This giant Isotelus trilobite is from the Ordovician of southern Ohio

strong flippers

Atractosteus strausi was an alligator gar

This dwarf mammoth tooth shows the ridges of enamel cemented by dentine

Helicoprion, whorl-tooth shark Dimorphodon This giant Isotelus trilobite isHelicoprion ("Spiral Saw") was a long lived genus of shark like cartilaginous fish that first arose in the oceans of the late Carboniferous 280 million years ago, survived the Permian Triassic Extinction Event, and eventually went extinct during the early Triassic some 225 million years ago. The only fossils known are the teeth, which were arranged in a fantastic "tooth whorl" strongly reminiscent of a circular saw. It was not until the discovery of