Cynosphenodon

Cynosphenodon (/ˌsaɪnəˈsfɛnədɒn/ SY-nə-SFEN-ə-don; "Dog Sphenodontian") is an extinct genus of rhynchocephalian in the family Sphenodontidae from the Middle Jurassic La Boca Formation of Tamaulipas, Mexico. It is known from a largely complete lower jaw and fragments of the upper jaw. It is suggested to be among the closest known relatives of the tuatara, with both being placed in the Sphenodontinae,^[1] which is supported by among other characters, the growth pattern of the teeth.^[2]

Cynosphenodon Temporal range: Middle Jurassic PreꞒ Ꞓ O S D C P T J K Pg N
Diagram of preserved skull elements
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Rhynchocephalia
Family:	Sphenodontidae
Genus:	Cynosphenodon Reynoso, 1996
Type species
†Cynosphenodon huizachalensis Reynoso, 1996

Cladogram after Simoes et al. 2022.^[3]

Sphenodontia	†Diphydontosaurus Eusphenodontia †Planocephalosaurus †Clevosaurus Neosphenodontia †Homoeosaurus †Pleurosauridae †Leptosaurus +†Kallimodon †Sapheosauridae Sphenodontidae †Eilenodontinae Sphenodontinae †Navajosphenodon †Cynosphenodon †Sphenofontis †Kawasphenodon Sphenodon (tuatara)

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