Ptychodus is a genus of extinct large durophagous (shell-crushing) 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. At least 16 species are considered valid, with the largest members of the genus suggested to have grown up to 10 meters long. The youngest remains date to around 85 million years ago. A large number of remains have been found in the former Western Interior Seaway.

The Lamniformes are an order of sharks commonly known as mackerel sharks. It includes some of the most familiar species of sharks, such as the great white, as well as more unusual representatives, such as the goblin shark and megamouth shark.