Scientists unearth one of the oldest known dinosaurs. Millions of years ago, a bloodthirsty dinosaur roamed Earth. The rough reptile terrorized its prey, viciously ripping apart animals with its sharp claws and knife-like teeth. Who was this fierce hunter? No, not Tyrannosaurus rex. It was Eodromaeus-a dinosaur the size of a dog!

Scientists recently introduced the teeny meanie, whichthey discovered in Argentina. That is a country in South America. Experts say Eodromaeus (ee-oh- DROH-mee-uhss) is one of the oldest dinosaurs ever discovered. It lived during the Triassic Period about 230 million years ago. The dinosaur's name means "dawn runner."

The pint-sized predator was four feet long from nose to tail and weighed less than fifteen pounds. Though Eodromaeus was small, it may hold big clues about the world's first dinosaurs."We're looking at a snapshot of early dinosaur life," says Paul Sereno. He is a paleontologist who helped find the reptile.

A Meaty History

Eodromaeus has a history that scientists can really sink their teeth into. The dinosaur was one of the very first theropods. A theropod was a meat-eating dino that walked on two legs.

The great-granddaddy of T. rex shared some key features with later carnivores, or meat eaters. The reptile had sharp, narrow teeth. "They have small, steak knife-like [edges] so that when they are jabbed into flesh, they open a wound," Sereno explained to WR News. Eodromaeusmost likely chowed down on small dinosaurs and the young of other reptiles.

Also, like later meat eaters, the dinosaur had hands that were perfect for grabbing its dinner. "The bones behind the claws are very long, so it can get the claw around something," Sereno explains. In addition, the end of the dino's tail was stiff to let Eodromaeus keep its balance while running.

The Big Reveal

Eodromaeus is helping scientists learn about other early dinosaurs. The reptile shared its turf with a similar-looking dinosaur called Eoraptor (ee-oh-RAP-tor). For years, experts suspected, or thought, that Eoraptor ate meat. But after comparing Eoraptor's and Eodromaeus's features, they determined that Eoraptor was an herbivore, or plant eater.

Despite the dinos' different diets, they had a lot in common, including their size, experts say. "I think if they [ran] by, you might not even know the difference except that one might want to rip your arm off and the other one might ... hide in a bush," Sereno says.

The fact that the dinosaurs shared so many features could mean that they are also very similar to the world's first dinosaur, Sereno says. Experts believe that dino roamed Earth ten million years earlier than Eoraptor and Eodromaeus did. That may seem like a long time, experts say, but it is relatively short compared with the 183 million years that dinosaurs existed.

Digging Deeper

Sereno and his team found both Eodromaeus and Eoraptor in northern Argentina. They believe the country may hold even more fossils-including the remains of the very first dinosaur.

"We're going to go back," Sereno says. He's pretty sure some fossils will turn up. "They always come out to say hi when we come!"

Profile of a Predator

Small animals, beware! Eodromaeus's skeleton shows certain features that are common in all meat-eating dinosaurs, including T. rex.
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