Tuatara Sphenodon punctatus with a prion chick, photographed by Paddy Ryan.

Belongs within: Lepidosauria.

The Sphenodontia are a clade of lizard-like reptiles that were abundant in the Triassic and Jurassic. They subsequently declined, and are represented in the modern fauna only by the tuatara Sphenodon species of New Zealand. Many extinct sphenodontians would have closely resembled the modern species, but Pleurosaurus from the Late Jurassic of Europe was an elongate aquatic reptile.

Synapomorphies (from Evans 1988): lacrimal bone absent; alternating acrodont teeth, seven or fewer premaxillary teeth on each side.

<==Sphenodontia [Sphenodontida]
    |  i. s.: AnkylosphenodonAN03
    |         GodavarisaurusS05
    |         *Sigmala sigmalaS05
    |         TingitanaS05
    |--Diphydontosaurus Whiteside 1986AN03, D07
    |    `--D. avonis Whiteside 1986V-RR99
    `--+--Planocephalosaurus robinsonaeE88, NB17
               |  i. s.: PiocormusE88
               |--+--Brachyrhinodon Huene 1910AN03, D07
               |  |    `--B. taylori Huene 1912B93
               |  `--Clevosaurus Swinton 1939AN03, S05 [=Glevosaurus Robinson 1973R73]
               |       |--*C. hudsoni Swinton 1939S05 [=*Glevosaurus hudsoniR73]
               |       |--C. bairdi Sues et al. 1994S05
               |       |--C. convallis Säilä 2005S05
               |       |--C. mcgilli Wu 1994S05
               |       |--C. minor Fraser 1988S05
               |       |--C. petilus Wu 1994S05
               |       `--C. wangi Wu 1994S05
                  |    |--Palaeopleurosaurus posidoniae Carroll 1985B93
                  |    `--Pleurosaurus Meyer 1831E88, D07
                  |         |--P. ginsburgi Fabre 1974B93
                  |         `--P. goldfussiN85
                  `--+--+--KallimodonAN03 [incl. LeptosaurusE88]
                     |  `--SapheosaurusAN03
                           |    |--ZapatadonAN03
                           |    `--+--CynosphenodonAN03
                           |       `--SphenodonAN03
                           |            |--S. guntheri Buller 1877WH02
                           |            `--S. punctatus (Gray 1842)WH02
                                |--OpisthiasAN03 [incl. TheretairusE88]
                                |    `--O. rarusAN03
                                     `--+--Eilenodon robustusAN03
                                        `--Priosphenodon Apesteguia & Novas 2003AN03
                                             `--*P. avelasi Apesteguia & Novas 2003AN03

*Type species of generic name indicated


[AN03] Apesteguia, S., & F. E. Novas. 2003. Large Cretaceous sphenodontian from Patagonia provides insight into lepidosaur evolution in Gondwana. Nature 425: 609–612.

[B93] Benton, M. J. 1993. Reptilia. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 681–715. Chapman & Hall: London.

[D07] Dixon, D. 2007. The Complete Illustrated Encyclopedia of Dinosaurs & Prehistoric Creatures. Hermes House: London.

[E88] Evans, S. E. 1988. The early history and relationships of the Diapsida. In: Benton, M. J. (ed.) The Phylogeny and Classification of the Tetrapods vol. 1. Amphibians, Reptiles, Birds pp. 221–260. Clarendon Press: Oxford.

[NB17] Nesbitt, S. J., R. J. Butler, M. D. Ezcurra, P. M. Barrett, M. R. Stocker, K. D. Angielczyk, R. M. H. Smith, C. A. Sidor, G. Niedźwiedzki, A. G. Sennikov & A. J. Charig. 2017. The earliest bird-line archosaurs and the assembly of the dinosaur body plan. Nature 544: 484–487.

[N85] Norman, D. 1985 (reprinted 2000). The Illustrated Encyclopedia of Dinosaurs. Salamander Books: London.

[R73] Robinson, P. L. 1973. A problematic reptile from the British Upper Trias. Journal of the Geological Society 129: 457–479.

[S05] Säilä, L. K. 2005. A new species of the sphenodontian reptile Clevosaurus from the Lower Jurassic of south Wales. Palaeontology 48 (4): 817–831.

[V-RR99] Vickers-Rich, P., T. H. Rich, G. C. McNamara & A. Milner. 1999. Is Agrosaurus macgillivrayi Australia’s oldest dinosaur? Records of the Western Australian Museum Supplement 57: 191–200.

[WH02] Worthy, T. H., & R. N. Holdaway. 2002. The Lost World of the Moa: Prehistoric life of New Zealand. Indiana University Press: Bloomington (Indiana).

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