Why is the tuatara unique?

Answer 1

The Tuatara are an endemic species of lizard found exclusively in New Zealand. Their body colouration is greenish-brown and grey. They grow to an adult length of around 31 inches (80 cm) from head to tail-tip, and can weigh up to 3lbs (1.3 kg).

See the related link to Wikipedia's excellent article on the species.

Answer 2

They are the only chordate reptile of the order Sphenodontia. The two living species of Sphenodontia are the only living in this order. Their most recent common ancestors is the squamates (lizards and snakes) and therefore they are of great interest in the evolution of early diapsids which included birds, dinosaurs and crocodiles. Their features resemble birds, crocodiles and turtles rather than the standard lizard. 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 photoreceptive eye dubbed the "third eye", whose current function is a subject of ongoing research, but is thought to be involved in setting circadian (rhythm within about 24 hours) and seasonal cycles.

Answer 3

The Tuatara's bite will cause serious injury and if you get too close they will bite.