Associated Press
WASHINGTON — For hundreds of generations, lumbering, long-necked dinosaurs came to the floodplain of a river in what is now Argentina, laid eggs in shallow dirt nests, spread some leaves over them and left.
It was a dinosaur style of parenthood that worked for millions of years — except when the nearby river flooded, says Luis Chiappe, a Los Angeles dinosaur expert.
Those floods drowned the unhatched baby dinos in their shells and buried them in mud. It was too bad for the dinosaurs but a scientific bonanza for Chiappe, chairman of the department of vertebrate paleontology at the Natural History Museum of Los Angeles County. The mud preserved and fossilized the eggs and embryos.
Chiappe, lead author of a study appearing today in the journal Science, said that at least six eggs from those flooded nests contain nearly intact baby dinos and are providing the most detailed look yet at a dinosaur from the last and most massive family of the long-necked plant-eaters.
The researchers report in Science that six embryos from the fossilized eggs have been identified as sauropods from the titanosaur family. This family included argentinosaur, thought to be the largest animal ever to walk the Earth at some 120 feet in length and weighing more than 80 tons.
Chiappe said some embryos found in the flooded nests are from a previously unknown species that is a smaller member of the same family but lived some 80 million years ago. All dinosaurs became extinct about 65 million years ago.
Sauropods include a number of species of plant-eating animals, all of which had small heads atop long necks and massive bodies that ended with muscular tails. The animals foraged among the tree tops and are thought to have lived in herds. Sauropods were among the most successful and diverse of the dinosaurs, appearing in different forms in the fossil record of nearly every continent starting almost 200 million years ago. The brontosaurus (now known as apatosaurus) is probably the most famous.
Chiappe said the eggs were about the size of softballs, and the six baby dinos analyzed were about a foot long. Fossil fragments of adults from the same species suggest that when fully grown, the babies would have been about 50 feet long.
"They grew about 50 feet in 15 to 20 years, which means they grew very, very fast," Chiappe said.
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