The Predator Dinogorgon

A quarter of a billion years ago, long before dinosaurs or mammals evolved, the 10-foot (3-meter) predator Dinogorgon, whose skull is shown here, hunted floodplains in the heart of today's South Africa. 
In less than a million years Dinogorgon vanished in the greatest mass extinction ever (the End-Permian Extinction, a/k/a "The Great Dying"), along with about nine of every ten plant and animal species on the planet.