But an ichthyosaur vertebra punctured by a broken-off pliosaurid tooth that was found moldering in a museum drawer has provided rare physical proof. It forever fossilizes a very violent moment in the prehistoric circle of life, showing how these ancient sea monsters lived. Photograph (left) and CT scan (right) of the pliosaurid tooth embedded in the vertebra of an ichthyosaur. “It had a huge mouth and huge, [Tyrannosaurus rex–like], banana-sized teeth crushing down on the thorax,” O’Keefe says. “I bet the head [of the ichthyosaur] fell off on one side and the tail fell off on the other.”