Tuataras are among the most evolutionarily distinct creatures in
the class Reptilia. Of the four orders of reptiles (Crocodilia,
Sphenodontia, Squamata, and Testudines), Sphenodontia (meaning
“wedge tooth”), is devoted entirely to the two living species of
tuatara, as well as many extinct species. Sphenodonts flourished
200 million years ago and diversified into a wide array of
creatures, such as aquatic pleurosaurs. Tuataras, however,
retain the ancient lizard-shaped body plan of tetrapods, though
they are only distantly related to squamates, the order of
reptiles that includes lizards. They used to be widespread
throughout New Zealand; however, their numbers declined with the
arrival of Polynesians and then Europeans, who brought cats,
dogs, and rats to the islands. Rats in particular have decimated
tuataras by eating their eggs, and tuataras can now only live on
remote islands off the coast of the main islands of New Zealand.
- Pronounced parietal eye – Tuataras, like many other chordates,
have a parietal