''Cynosphenodon'' ( ; "Dog Sphenodontian") is an extinct genus of the family

Sphenodontidae Sphenodontidae is a family within the reptile group Rhynchocephalia, comprising taxa most closely related to the living tuatara of the genus ''Sphenodon''. Historically the taxa included within Sphenodontidae have varied greatly between analyse ...

from the Middle Jurassic La Boca Formation of

Tamaulipas Tamaulipas (), officially the Free and Sovereign State of Tamaulipas ( es, Estado Libre y Soberano de Tamaulipas), is a state in the northeast region of Mexico; one of the 31 states which, along with Mexico City, comprise the 32 Federal Entiti ...

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

. Growth patterns in the teeth of ''Cynosphenodon'' suggest its close relationship with the modern

tuatara Tuatara (''Sphenodon punctatus'') are reptiles endemic to New Zealand. Despite their close resemblance to lizards, they are part of a distinct lineage, the order Rhynchocephalia. The name ''tuatara'' is derived from the Māori language and m ...

.Reynoso, V. H. (2003). Growth patterns and ontogenetic variation of the teeth and jaws of the Middle Jurassic sphenodontian ''Cynosphenodon huizachalensis'' (Reptilia: Rhynchocephalia). ''Canadian Journal of Earth Sciences 40''(4), 609–619

References

Jurassic lepidosaurs Sphenodontia Fossils of Mexico Prehistoric reptile genera {{Jurassic-reptile-stub