- NEW YORK (AP) -- Scientists have found a vast dinosaur nesting site in
Argentina that includes thousands of fossil eggs. Inside egg fragments,
they found the first embryo remains from a major class of large dinosaurs,
and the first definite fossils of embryo skin from any dinosaur.
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- Discoveries from the site should shed
light on the early development of sauropods, a class of plant-eaters with
long necks and tails, small heads and four elephant-like legs that included
the biggest animals ever to walk the Earth.
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- The badlands site, which covers a square
mile, is littered with dark-gray fossil fragments of round, rough-textured,
six-inch eggs. "You see eggshells everywhere," said Luis Chiappe
of the American Museum of Natural History in New York.
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- The eggs were laid 70 million to 90 million
years ago, apparently by titanosaurs that stretched about 45 feet long.
The hatchlings might have been only about 15 inches long.
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- From the embryonic remains, "we're
really getting a look at what these animals would have looked like to us,
and felt like to touch, when they hatched," said Lowell Dingus of
the museum.
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- Chiappe, Dingus and others describe the
finds in Thursday's issue of the journal Nature.
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- Scientists found so many embryonic remains
that it appears catastrophe struck the nesting ground, keeping many eggs
from hatching, Chiappe said. Floods may have penetrated the porous shells
and drowned the embryos, he said. The flooding also could have carried
in layers of silt that kept the eggs so well-preserved.
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- The modern-day result are embryonic bones,
which look like tiny light brown flakes surrounded by green mudstone in
eggshell fragments, and dark patches of fossilized skin within the shells.
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- The haul includes 70 or so shell fragments
containing pieces of fossilized skin, in fingernail-sized patches or smaller,
their scales clearly visible. No complete embryo skeletons were found,
but even finding the collapsed bones is a rarity. Before the new find,
embryonic remains had been identified from only five species of dinosaur.
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- "If you're a dinosaur paleontologist,
then I think it's a pretty exciting and wonderful discovery," said
Kenneth Carpenter of the Denver Museum of Natural History, who was familiar
with the work.
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- For one thing, it knocks down a controversial
suggestion that sauropods gave live birth, Carpenter said. That idea had
arisen because sauropod fossils are common in some older rocks in North
America, yet no remains of eggs had ever been found.
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- And the sheer number of eggs at the site
suggests dinosaurs converged repeatedly in one place to lay them, Carpenter
said. While scientists have speculated about such behavior, "we've
never had any real good evidence that's what dinosaurs would do,"
he said.
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- The discovery also shows that a particular
kind of large round dinosaur egg found in Africa, India, China, Europe
and South America is often from sauropods, Chiappe said. Carpenter said
that had been proposed before because the eggs were so big, but that the
new discovery finally solves the mystery after about 100 years.
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- The site was discovered a year ago in
Neuquen, a province in northwestern Patagonia.
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