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]

v t e Rhynchocephalia
Kingdom: Animalia Phylum: Chordata Class: Reptilia Superorder: Lepidosauria Sauropsida see Sauropsida Lepidosauromorpha see Lepidosauromorpha Rhynchocephalia see below↓ Rhynchocephalia
†Gephyrosauridae? Gephyrosaurus Penegephyrosaurus Deltadectes Sphenodontia †Diphydontosaurus †Godavarisaurus †Micromenodon †Pelecymala †Rebbanasaurus †Sphenocondor Incertae sedis †Paleollanosaurus †Whitakersaurus Acrosphenodontia †Planocephalosaurus †Godavarisaurus? Eusphenodontia †Lanceirosphenodon †Microsphenodon †Opisthiamimus †Polysphenodon †Clevosauridae Brachyrhinodon Clevosaurus Polysphenodon? Neosphenodontia †Colobops? †Homoeosaurus †Lanceirosphenodon? †Pamizinsaurus †Rebbanasaurus? †Sphenocondor? †Theretairus †Zapatadon †Kallimodon †Leptosaurus †Sapheosauridae Piocormus Sapheosaurus Oenosaurus "Eupropalinal sphenodonts" †Lamarquesaurus †Sigmala †Tingitana †Vadasaurus †Pleurosauridae? Palaeopleurosaurus Pleurosaurus Tingitana? Vadasaurus? Sphenodontidae †Ankylosphenodon †Cynosphenodon †Derasmosaurus †Kawasphenodon? †Navajosphenodon †Pamizinsaurus? Sphenodon †Sphenofontis †Sphenovipera? †Theretairus? †Tika †Zapatadon? †Opisthodontia Fraserosphenodon Kawasphenodon? Opisthias Pelecymala? Trullidens Pleurosauridae? Sapheosaurs? Eilenodontinae Eilenodon Kaikaifilusaurus Patagosphenos Priosphenodon Sphenotitan? Toxolophosaurus