Ptychodus is a genus of extinct large durophagous lamniform sharks from the Cretaceous period, spanning from the Albian to the Campanian. Fossils of Ptychodus teeth are found in many Late Cretaceous marine sediments worldwide. From Wikipedia
Newly discovered fossils from the Cretaceous period show that the giant Ptychodus sharks had a diet primarily consisting of hard-shelled prey, contrasting with modern sharks.
