FOR KIDS: Eating Meat Way Before T. Rex - Science News

FOR KIDS: Eating Meat Way Before T. Rex - Science News

FOR KIDS: Eating meat way before T. rex
Fossil find uncovers traits of some of earliest dinos
By Stephen Ornes
Web edition : Wednesday, January 26th, 2011
font_down font_up Text Size
access
Enlargemagnify
Pint-sized meat-eaterThis illustration shows what Eodromaeus might have looked like. It weighed only 10 to 15 pounds and measured about 4 feet in length from snout to tail tip. Univ. of Chicago, copyright Todd Marshall

About 230 million years ago, what is now a park in northern Argentina was a popular neighborhood for some of the earliest dinosaurs. The area is called the Valley of the Moon, though Paul Sereno, a paleontologist at the University of Chicago, uses a different term.

“What we have is this unbelievable graveyard of the earlier dinosaurs,” Sereno told Science News. “We don’t have a lot of places like this.”

A team of paleontologists, including Sereno, recently identified a new type of dinosaur, based on fossils found in the area. They named the new species Eodromaeus, which means “dawn runner.” The creature was long and lean, about four feet from teeth to tail, and weighed about 10 or 15 pounds. Its sharp teeth and long fingers suggest it ate other animals.

The scientists say the Eodromaeus belonged to the group of dinosaurs called theropods, which were meat-eaters that walked on two feet . A more familiar, and much larger, example of a theropod is the Tyrannosaurus rex. However, the T. rex didn’t rule the land until hundreds of millions of years after Eodromaeus.
access
Enlargemagnify
Early dinoPaleontologist Paul Sereno says Eodromaeus dates to the beginning of the dinosaur era, about 230 million years ago. Univ. of Chicago, copyright Mike Hettwer

Most types of dinosaurs vanished from Earth about 65 million years ago. (They are not completely gone: Birds are descended from dinosaurs.) Scientists like Sereno, however, want to know how dinosaurs got started. On Earth, life is always changing, or evolving. All living organisms on Earth evolve over hundreds and millions of years, with every generation slightly different from the one before. Paleontologists want to know how dinosaurs evolved.

Fossils from the Valley of the Moon may provide clues. In 1991, the paleontologists working there had discovered a dinosaur called Eoraptor, which lived in the same neighborhood as Eodromaeus and was about the same size and shape. However, Eodromaeus ate meat, and Eoraptor ate plants. In other words, they weren’t the same dinosaur, but they probably weren’t too far apart on the dinosaur family tree. Eventually, though, they went separate ways. The descendants of Eodromaeus became giant meat-eaters like T. rex. The descendants of Eoraptor, on the other hand, ate plants. (Eoraptor is an example of another large group of dinosaurs, the sauropods.)

Sereno told Science News the two types of dinosaurs looked so similar they would be easy to confuse. “From 20 feet away you’d do a double take — will the animal run from you or take your leg off?” he said.

The scientists have reported on other fossils found in the Valley of the Moon. These fossils will help paleontologists piece together the puzzle of how dinosaurs evolved, according to Ricardo Martinez, the paleontologist at the National University of San Juan in Argentina who led the most recent study.
access
Enlargemagnify
Fossil troveThe fossils were found in the Valley of the Moon in northwestern Argentina.Univ. of Chicago, copyright Ricardo Martinez

“The new dinosaur is special for sure, but we also have the first step of the radiation of the dinosaur story,” Martinez told Science News. In evolution, the word radiation (or, more often, adaptive radiation) refers to different species evolving from a common ancestor. Eodromaeus and Eoraptor dinosaurs evolved from the same ancestor, but their descendants became wildly different species. Because the dinos were so closely related, Martinez says, their fossils can be used to study dinosaur evolution — and help scientists figure out how dinosaurs got started, long before they dominated the land.

In recent decades, the rate of dinosaur discovery has gone up, and each new discovery brings information about these ancient animals — and more questions. In a study published five years ago, mathematicians estimated there are more new types of dinos fossilized in the Earth, waiting to be discovered, than have already been found. It’s a good time to become a dinosaur hunter.

POWER WORDS (adapted from the Yahoo! Kids Dictionary)

paleontology The study of the forms of life existing long before humans, in prehistoric or geologic times. These life forms are understood by studying what is left of them: the fossils of plants, animals and other organisms.

species A fundamental category for grouping and organizing different life forms based on their physical and behavioral traits. A species consists of related organisms capable of interbreeding. This taxonomic classification is the most specific and ranks below genus or subgenus.

adaptive radiation The process by which a dominant group or species over time divides into smaller groups, each small group having traits for thriving in specific environments.

ancestor The actual or hypothetical organism or stock from which later kinds of organisms evolve.

hypothetical Based on a hypothesis, which is a proposed explanation for an observed phenomenon or scientific problem.

Share this post