Eggs Hold Skulls of Titanosaur Embryos

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Chiappe and his colleagues report on their findings in the September 28th issue of the journal Science.

Other Clues From Nesting Site

The bodies of all sauropods were similar, Carrano explained. These dinosaurs were huge, walked on four legs, and had very long heads and tails.

The head is often the key to identifying one species from another. Skulls also reveal a lot about the diet and feeding habits of a particular dinosaur group, Carrano said.

Titanosaurs were very common between 90 and 65 million years ago and lived on all the continents except Antarctica and Australasia. They were more robust than brachiosaurus but had shorter tails, a broader and more elongated head, pencil-like teeth, and scaly armored skin. Some of the larger titanosaurs reached lengths of up to 120 ft (36 meters) and weighed 80 to 100 tons, according to Chiappe.

The fossils are not the only clues to the prehistoric world. Nests like those in which the embryo skulls were found also offer details about the age of the site, the environment, and climate during the time when these dinosaurs roamed.

The number and distribution of eggs found in Auca Mahuevo suggest that hundreds of female titanosaurs gathered at this nesting site, dug holes in the dirt, laid eggs, and covered their clutch with vegetation, said Chiappe.

The rock containing the six eggs is between 79 and 83 million years old. The eggs appear to have been deposited before a seasonal flood, which buried them gently as muddy water trickled into the plant-covered nests without removing any of the vegetation.

The team of researchers said they were not able to determine which species of titanosaur the embryos represent.

Many fossils belonging to new species have been found at the Auca Mahuevo site in recent years, said Carrano. "I wouldn't be surprised if these also turned out to be a completely new species," he said. "Either way, it is a fantastic find and is sure to yield important evolutionary insights."

This story will be aired in the United States on September 27 on the television news show National Geographic Today.

Recent National Geographic News stories on dinosaurs:
Dinosaur Beak Probably Used to Strain Food, Not Kill Prey
Study Paints New Picture of Dinosaur's Nose
Skeleton of New Dinosaur "Titan" Found in Madagascar
"Tidal Giant" Roamed Coastal Swamps of Ancient Africa
"Feathered" Fossil Bolsters Changing Image of Dinosaurs
Oddly Angled Teeth Make Masiakasaurus Stick Out

Additional dinosaur resources from National Geographic:
Paul Sereno: NG Explorer-in-Residence and dinosaur hunter
Wanted: Albertosaurus
Dinosaur Eggs
Destinations: Dinosaur National Monument
Educational Video: Dinosaurs on Earth: Then and Now
Children's Pop-up Book: Dinosaur Babies

Related lesson plan:
Use this National Geographic News article in your classroom with the Xpeditions lesson plan: Physical Characteristics of Places: The Fossil Record

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