Fragments previously referred to "Platypterygius" have been found to be from several different taxa. While the front of the lower jaw is typically low, its rear depth is very variable. Traditionally, ichthyosaurs were seen as decreasing in diversity even further with the Cretaceous , though they had a worldwide distribution. Some early ichthyosaurs were durophagous and had flat convex teeth adapted for crushing shellfish. The demise of the ichthyosaurs has been described as a two-step process.
nest...