Helicoprion, whorl-tooth shark Pachycephalosaurus With a body mass greater

With a body mass greater than most large ungulates (horses

straight teeth

These mounds generally ranged in size from 20 to 300 feet (91 m) in diameter and served as burial structures

Agriotherium was about 9 feet in body length

and which may have been used for species or sexual identification

Helicoprion, whorl-tooth shark Pachycephalosaurus With a body mass greaterHelicoprion ("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