Helicoprion, whorl-tooth shark Dilophosaurus Lake Uinta was the longest

Lake Uinta was the longest lived

The Placoderms are divided into two groups (arthodires and antiarchs)

or even a separate kingdom of life unrelated to anything living today

This real dinosaur bone is about 65 million years old and is from the Hell Creek Formation

It wasn't until almost 50 years after the discovery of the type specimen that it was formally classified into its own family

Helicoprion, whorl-tooth shark Dilophosaurus Lake Uinta was the longestHelicoprion ("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