Ankylosphenodon is an extinct species of sphenodontian known from Tepexi de Rodriguez, Mexico.^[1] It is known from Early Cretaceous sedimentary deposits from the Tlayua formation.^[1]

Ankylosphenodon is thought to have been an aquatic reptile due to its pachyostotic skeleton and other anatomical features often seen in aquatic animals.^[1] There is also evidence that its teeth were constantly growing throughout its lifetime, which may be indicative of herbivory, a rare characteristic among Lepidosauria.^[1]