The tuatara (<i>Sphenodon punctatus</i>, left) is one of only two surviving species in the clade Sphenodontia.

<p>The sister clade to the tuatara is Squamata, which includes the ∼7,000 living species of snakes and lizards, including the ornate day gecko (<i>Phelsuma ornata</i>, right). (Left) from Wikimedia commons, taken by user KeresH, <a href="http://commons.wikimedia.org/wiki/File:Henry_at_Invercargill.jpg" target="_blank">http://commons.wikimedia.org/wiki/File:Henry_at_Invercargill.jpg</a>; (Right) by the author.