"Nasty" Little Predator From Dinosaur Dawn Found

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Scientists have discovered a new dinosaur species at the foot of South America's Andes mountains. The long-necked Eodromaeus, or "dawn runner," searched for prey as the age of dinosaurs began, approximately 230 million years ago.

© 2011 National Geographic; Photos, video and illustration courtesy of University of Chicago

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Researchers have uncovered a new, pint-sized dinosaur that may give paleontologists a better idea of how dinosaurs evolved from their earliest days.

The long-necked Eodromaeus, the “dawn runner,” was about 4 feet long, and weighed only 10 to 15 pounds. It was a carnivore, and a fast runner.

Two individual skeletons were found side-by-side in the foothills of the Andes Mountains in Argentina, in an area known as the “Valley of the Moon.”

National Geographic Explorer-in-Residence Paul Sereno says this discovery gives scientists the ‘earliest look’ at the development of the dinosaurs.

SOUNDBITE: Paul Sereno, Paleontologist, University of Chicago:“It was a bi-pedal, two-legged predator. It chased down its prey, grabbed onto it with nice, grasping hands, and munched on it with re-curved teeth for slicing flesh. It is the best view we have of where the predatory lineage comes from- where ultimately the descendants like Tyrannosaurus Rex where they began.”

Radioisotopes place the age of the new species’ skeletons at about 230 million years old.

Sereno and the report’s lead author, Ricardo Martinez of Argentina’s National University of San Juan, describe their team’s findings in the January 14th issue of the journal Science.

Martinez calls the find the “single best view we have of the birth of the dinosaurs.”

The area in which Eodromaeus was found was once a rift valley in the southwest corner of the supercontinent Pangea. Volcanoes, over time, spewed ash into the valley, and sediments covering the skeletons accumulated a thickness of more than 2000 feet.

SOUNDBITE: Paul Sereno, Paleontologist, University of Chicago: “Today, we can look at it as a mounted skeleton, we can actually put flesh on it. This is the most complete picture we have of what a predatory dinosaur lineage – what it looked like at the very beginning. It was small, but nasty. This animal was fast.”

Eodromaeus is believed to be a precursor to later meat-eaters called theropods, and eventually to birds

http://news.nationalgeographic.com/news/2011/01/110113-eodromaeus-dinosaur-discovery-vin-video/

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Pictures: "Nasty" Little Predator From Dinosaur Dawn Found



Eodromaeus: Nasty, Brutish, and Short

Photograph courtesy Mike Hettwer

Deadly and dog-size, the dinosaur Eodromaeus (shown in reconstruction) lived in Argentina 230 million years ago, a new study says. The new species is providing fresh insight into the era before dinosaurs overtook other reptiles and ruled the world, a new fossil study says. (Watch video.)

"This is the most complete picture we have of what a predatory dinosaur lineage – what it looked like at the very beginning," said study co-author Paul Sereno. "It was small but nasty—this animal was fast."

One of the earliest known dinosaurs, Eodromaeus was only about 4 feet (1.3 meters) long and would have barely reached the knees of an adult human. But this unassuming little dinosaur gave rise to the theropods, including Tyrannosaurus rex and the "terrible claw," Deinonychus, the new study suggests.

Like those fearsome descendants, Eodromaeus had a long rigid tail, a unique pelvis shape, and air sacs in its neck bones that may have been related to breathing—and which add to evidence that theropod dinosaurs eventually evolved into today's birds.

(Take a dinosaur quiz.)

—Ker Than

Published January 13, 2011

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Hold Me Closer, Tiny Dinosaur

Photograph courtesy Mike Hettwer

Needle-like teeth spike a full-size replica of the skull of the new Eodromaeus dinosaur, held by University of Chicago paleontologist Paul Sereno, also a National Geographic explorer-in-residence. (The National Geographic Society owns National Geographic News.)

Eodromaeus lived alongside—and now appears to have, in a sense, taken the place of—a very similar dinosaur species, Eoraptor (picture), Sereno said. "If you went back 230 million years ago and one of these creatures flitted by, you'd have to wonder which one it was."

Sereno and his team once thought Eoraptor was an ancestor of meat-eating dinosaurs. But due to recent analysis of Eoraptor fossils, as well as the discovery of Eodromaeus, he now thinks Eoraptor was an ancestor of the giant, long-necked, plant-eating dinosaurs called sauropods.

"That's the beauty of dinosaur origins," Sereno said. "Who could predict that these 10- to 15-pound [4.5- to 7-kilogram] creatures—both looking quite similar but eating different things—would end up evolving into things  as disparate as Diplodocus and Tyrannosaurus?"

The reclassification of Eoraptor makes sense, agreed Hans-Dieter Sues, a dinosaur expert at the National Museum of Natural History in Washington, D.C., who was not involved in the study.

"One thing that everyone noticed when Eoraptor was first discovered was that the back teeth were very odd-looking for a theropod," said Sues, also a contributing editor to the National Geographic News Watch blog. "It had these little leaf-shaped teeth in the back, and those are teeth you don't really find in theropods."

(Related: "Smallest Meat-Eating Dinosaur in North America Discovered.")

Published January 13, 2011

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Complete Set

Photograph courtesy Mike Hettwer

Nearly all of the bones of Eodromaeus (pictured in a replica skeleton) have been accounted for—considered remarkable for such a small creature.

Based on its fossils, scientists think Eodromaeus, like its theropods descendents, stood and ran on two legs and had sharp teeth and grasping claws, which the new dinosaur used to snatch the young of other reptiles.

University of Maryland Paleontologist Thomas Holtz agreed that Eodromaeus is likely an early theropod ancestor.

"I think they've got a good case for it here," said Holtz, who wasn't part of the new study. "In terms of characteristics, it does seem to be very, very low in the theropod family tree."

It's not too surprising that Eodromaeus and Eoraptor looked very similar, he added. Both shared a common ancestor only about ten million years before, which in evolutionary terms is not a very long time.

"The closer we get to the common ancestor, the less time they've had to diverge, so they look a lot more like each other," he said. "If you go back far enough, eventually they're the same creature."

(Pictures: Oldest Dinosaur Embryos Show "Big Surprises."

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Published January 13, 2011

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Valley of the Dawn Runner

Photograph courtesy Ricardo Martinez

The desolate Valley of the Moon in northwestern Argentina, where fossils of Eodromaeus and Eoraptor were found, was filled with lush forests 230 million years ago, according to the study co-author Sereno. "It was a gorgeous environment."

(Related: "New T. Rex Cousin Suggests Dinosaurs Arose in South America.")

Eodromaeus and Eoraptor shared this Triassic paradise with various other groups of reptiles, including parrot-beaked reptiles that were distantly related to dinosaurs, protomammals, and a number of large crocodile-like creatures.

Studying the shared traits that Eodromaeus and Eoraptor could help scientists paint a picture of the unknown last common ancestor of all dinosaurs, the University of Maryland's Holtz said.

That dinosaur Eve, Holtz said, "was probably bipedal, its hands may have already been adapted for grasping ... and its diet may not have been strictly meat or plants." By contrast, "the first dinosaurs may have been omnivores."

The new Eodromaeus dinosaur fossils are detailed and analyzed in this week's issue of the journal Science.

Published January 13, 2011