Fossil Egg Finds Yield Clues to How Pterosaurs Lived

December 2, 2004

The discoveries of two fossilized eggs from the ancient flying reptiles known as pterosaurs were announced Wednesday. The finds raise to three the number of known pterosaur eggs—the one other known egg was only announced last summer.

Until very recently, scientists wondered if the reptiles that filled the skies in the age of the dinosaurs laid eggs or gave birth to live young like mammals do.

"We've [now] got really strong evidence that pterosaurs laid eggs," said Christopher Bennett, a pterosaur expert at Fort Hays State University in Hays, Kansas. Bennett was not involved with the discoveries.

The first pterosaur egg, discovered in China, was announced in the journal Nature in June. A second egg from China and one from Argentina are reported in today's edition of the journal.

Fossil Eggs

Luis Chiappe is the curator of vertebrate paleontology at the Natural History Museum of Los Angeles County in California and lead author of the paper on the Argentine egg. He said the timing of the discoveries is "just a coincidence" but added that it is "amazing."

The egg from Argentina is about a hundred million years old and thought to have had a hard shell similar to those of birds and dinosaurs. Chiappe identified the egg as belonging to the flamingo-like Pterodaustro guinazui. He said the discovery firms up evidence for the species' communal lifestyle.

"Our egg was found amongst a bunch of other fossils of the same species, fossils ranging from hatchlings to teenagers to full adult individuals. … That tells us these animals nested in a colony and offered to their young parental care," he said.

Qiang Ji of Nanjing University in Nanjing, China, and colleagues described the new egg from China. The egg is about 121 million years old and reported to have had a "soft and leathery" shell similar to crocodile and turtle eggshells.

Bennett, who has reviewed the papers describing the fossils, said the eggshells of both were very thin and consistent with each other in shape and form.

"From what's available there's no evidence we have two different types of eggshell here, and I would be surprised if we did," he said. "If there was clear evidence one was hard like a chicken egg and the other soft and leathery, that would be surprising to me."

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