New Zealand's tuatara is no lizard—it is the last of its order
Sphenodon punctatus looks lizard-like yet is the sole living rhynchocephalian, a once-diverse order that appears in Middle Triassic rocks about 244–241.5 million years ago. Endemic to New Zealand, tuatara can reach 80 cm and 1.3 kg, with a spiny crest and a second upper tooth row on the palate.
The Māori name means "peaks on the back," after the spiny crest of soft skin folds that males can stiffen for display. Science took decades to place the animal. When the British Museum received a skull in 1831 it was filed as a lizard, and John Edward Gray coined Sphenodon, Greek for "wedge tooth." Only in 1867 did Albert Günther spot features shared with birds, turtles and crocodiles and erect the order Rhynchocephalia, "beak head," for the tuatara and its fossil kin.
That order first shows up in England's Middle Triassic, about 244 to 241.5 million years ago, and by the Jurassic its members were the world's dominant small reptiles, including swimming pleurosaurs and plant-eating forms. They faded through the Cretaceous; the last one outside New Zealand lived in Patagonia around 66 to 60 million years ago. Calling the tuatara a "living fossil" is now discouraged, because no continuous fossil series shows it unchanged since those Mesozoic days.
The anatomy is distinctive. A fully closed lower temporal bar is thought to brace the skull during biting. The teeth are fused to the top of the jawbone, have no roots and are never replaced, so worn-down elderly tuatara must switch to soft food such as slugs and earthworms. A second row on the palate lets the lower teeth slot between two upper rows, and the jaw then slides forward to shear chitin and bone. Each eye focuses on its own, and five visual opsin genes hint at good colour vision even in dim light.
Adult males reach about 61 cm and 1 kg, females about 45 cm and 0.5 kg, making them New Zealand's largest reptiles. Protected since 1895, they had vanished from the mainland under habitat loss and the Polynesian rat, surviving on 32 offshore islands. A release into the fenced Zealandia sanctuary in 2005 changed that, and a nest found there in late 2008 marked the first known wild breeding on the North Island in more than 200 years.
Source: Tuatara
