A TREASURE trove of South American fossils helps to explain the survival of the enigmatic tuatara, a reptile sometimes called a 鈥渓iving fossil鈥�.
Surviving only on some of New Zealand鈥檚 smaller islands, the tuatara (above) is the sole living member of the sphenodontians, an ancient family of primitive reptiles. These appeared across North America and Europe more than 200 million years ago, and supposedly disappeared 110 million years ago, when the lizards came to dominate.
Now Sebasti谩n Apesteguia and Fernando Novas of the Argentine Museum of Natural History in Buenos Aires report that sphenodontians survived considerably longer on southern continents, which were then still joined to New Zealand. They discovered sphenodontian fossils in a quarry at Cerro Polic鈥檃 in southern Argentina which reveal the beasts were abundant 90 million years ago. Undescribed fossils from another site show they survived till near the end of the Cretaceous period 65 million years ago (Nature, vol 425, p 609).
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The Cerro Polic鈥檃 fossils of Priosphenodon are particularly stunning, says Susan Evans of University College London. At 1 metre long, twice the length of a tuatara, it is the largest known terrestrial sphenodontian. 鈥淚t鈥檚 fabulous material, beautifully preserved in three dimensions,鈥� says Evans.