tuatara

Male tuatara Conservation status

Vulnerable (IUCN 2.3) Scientific classification Kingdom: Animalia

Phylum: Chordata

Subphylum: Vertebrata

Class: Reptilia

Order: Rhynchocephalia

Family: Sphenodontidae

Genus: Sphenodon

Gray, 1831

dark red: range (North Island, New Zealand) Species Sphenodon guntheri - (Buller, 1877) Sphenodon punctatus - (Gray, 1842) Sphenodon diversum - Colenso, 1885 †

The tuatara is a reptile endemic to New Zealand which, though it resembles most lizards, is actually part of a distinct lineage, order Sphenodontia.[1][2] The two species of tuatara are the only surviving members of its order, which flourished around 200 million years ago.[2] Their most recent common ancestor with any other extant group is with the squamates (lizards and snakes). For this reason, tuatara are of great interest in the study of the evolution of lizards and snakes, and for the reconstruction of the appearance and habits of the earliest diapsids (the group that also includes birds and crocodiles).

Tuatara are greenish brown, and measure up to 80 cm (32 in) from head to tail-tip[3] with a spiny crest along the back, especially pronounced in males. Their dentition, in which two rows of teeth in the upper jaw overlap one row on the lower jaw, is unique among living species. They are further unusual in having a pronounced parietal eye, dubbed the "third eye", whose current function is a subject of ongoing research. They are able to hear although no external ear is present, and have a number of unique features in their skeleton, some of them apparently evolutionarily retained from fish. Although tuatara are sometimes called "living fossils", recent taxonomic and molecular work has shown that they have changed significantly since the Mesozoic era.

The tuatara has been classified as an endangered species since 1895[4][5] (the second species, S. guntheri, was not recognised until 1989).[3] Tuatara, like many of New Zealand's native animals, are threatened by habitat loss and the introduced Polynesian Rat (Rattus exulans). They were extinct on the mainland, with the remaining populations confined to 32 offshore islands,[2] until the first mainland release into the heavily fenced and monitored Karori Wildlife Sanctuary in 2005.[6]

The name "tuatara" derives from the Maori language, and means "peaks on the back".[7] As with many other Maori loanwords, the plural form is now generally the same as the singular in formal New Zealand English usage. "Tuataras" remains common in less formal speech, particularly among older speakers. Contents [hide] 1 Taxonomy and evolution 1.1 Species 2 Description 2.1 Skull 2.2 Sensory organs 2.3 Spine and ribs 3 Behaviour 4 Reproduction 5 Conservation 5.1 Distribution and threats 5.2 Eradication of rats 5.3 Introductions 5.3.1 Brothers Island tuatara 5.3.2 Northern tuatara 5.4 Captive breeding 6 Cultural significance 7 References 8