The tuatara (Sphenodon punctatus) can grow to lengths of 60 centimetres.
The tuatara of New Zealand (Sphenodon punctatus; pictured), formerly thought to be a lizard, was recognized 150 years ago this month as the only living member of its own reptile group — Rhynchocephalia (595–629; 1867). Phil. Trans. R. Soc. 157,
The tuatara's ancestors separated from those of lizards and snakes (Squamata) around 240 million years ago. The frame-like skull of S. punctatus, long believed to be an archaic feature, is in fact a specialization for supporting its powerful jaws (379–430; 1986). Phil. Trans. R. Soc. Lond. B 312,
The animal's taxonomic isolation has turned it into a flagship species for studies of evolution, biodiversity and conservation (see, for example, A. Cree Tuatara Canterbury Univ. Press; 2014).