Ancient, Lizard-Like Reptile Discovered

John Roach
for National Geographic News
October 8, 2003

A pair of Argentine paleontologists have discovered numerous 90-million-year-old fossils of a new type of sphenodontian—an ancient lizard-like reptile thought to have gone extinct about 120 million years ago except for a few relicts that live today in New Zealand, the tuatara.

The fossils, including several well-preserved skulls, were found in the red sandstone cliffs of the La Buitrera fossil quarry in northwestern Patagonia, about 800 miles (1,300 kilometers) east of Buenos Aires.

The new species, Priosphenodon avelasi, had a blunt head, a sharp eagle-like beak, long arms, and wielded square claws. It was about three feet (one meter) long and weighed an estimated 33 pounds (15 kilograms), making it bigger than any known terrestrial sphenodontian.

The Argentine paleontologists say the discovery of Priosphenodon helps fill a gap in the fossil record between the Early Cretaceous sphenodontians and their living relatives in New Zealand.

"Priosphenodon was not a minor component in the terrestrial faunas of South America," said Sebastián Apesteguía, a vertebrate paleontologist at the Argentine Museum of Natural History in Buenos Aires. "It is the most abundant species of the fossil assemblage."

Other bones collected at La Buitrera (The Vulture Cage) include crocodiles, snakes, and additional remains of one of the largest carnivorous dinosaurs that ever evolved: an eight-ton, 12-foot (3.7-meter) tall, meat-eating, dagger-toothed creature named Giganotosaurus.

Apesteguía and his colleague Fernando Novas, also at the Argentine Museum of Natural History, report on their discovery in the October 9 issue of Nature.

Robert Carroll, a vertebrate paleontologist at McGill University in Montreal, Canada, said the discovery of Priosphenodon raises broad questions about why this group of sphenodontians was so successful in the Cretaceous.

"There is a lot to be learned from South America of vertebrates of all groups," he said.

New Lessons

Before this discovery, scientists believed that the wide appearance of lizards and snakes in the Early Cretaceous fossil record (about 120 million years ago) signified a change that caused sphenodontians to become much less diverse.

"The history was apparently distinct during the Cretaceous of South America," said Apesteguía. "Although the record is still patchy, South American lizards lived with sphenodontians as a minor component of a crocodile-dominated fauna."

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