Ankylosphenodon

Ankylosphenodon is an extinct genus of sphenodontian known from multiple specimens recovered from the Early Cretaceous deposits of the Tlayúa Formation, near Tepexi de Rodriguez, Mexico. It is likely part of a sphenodontid lineage that also includes Eilenodon and Toxolophosaurus, though has similarities to the sapheosaur clade. Its skeleton is pachyostotic (thickened) skeleton, believed to be an adaptation for a semi-aquatic lifestyle. Its teeth appear to have grown continuously, like in rodents.