Feathery find: scientists unearth evidence that some dinosaurs sported feathers

DID YOU KNOW?

* In early 2005, fossil hunters in China uncovered the preserved remains of a tiny dinosaur inside the belly of a fossilized mammal. Before this find, scientists thought it was unlikely that mammals could attack and eat a dinosaur.

* A second fossil--found at the same site as the one containing the eaten dinosaur--is the largest early mammal ever found. It is about the same size as a modern-day dog.

CRITICAL THINKING:

* How might the information you gather from trace fossils, such as footprints, differ from the information you gather from replacement fossils, which form when minerals replace an organism's bones?

CROSS-CURRICULAR CONNECTIONS:

COMPUTER SCIENCE: Imagine you are a paleontologist on a dig in Liaoning Province. You stumble across an unusual fossil that will stun the world. Create a PowerPoint presentation to show your classroom of "fellow scientists" how you found your fossil and what's so special about it.

RESOURCES

* Dinosaurs: Ancient Fossils, New Discoveries will be on exhibit at the American Museum of Natural History in New York City from May 14, 2005 until January 8, 2006. Then, it will travel around the country. To find an exhibition location near you, check out this Web site: www.amnh.org/exhibitions/dinosaurs/

Today, northeastern China's Liaoning (lyee-yow-ning) Province is dotted with traditional mud houses and a patchwork of fields growing a corn-like crop called sorghum. But turn back the clock 130 million years to the Cretaceous Period, and dinosaurs dominated the landscape. That's why, for a fossil hunter looking for prehistoric dinosaur remains, no place beats Liaoning. There, an incredible diversity of animals and plants were buffed beneath a blanket of volcanic ash that had spewed from nearby volcanoes. This sooty coating perfectly preserved their bones, teeth, and sometimes even their skin.

Now, this ancient past beckons scientists from around the world. Their hope? That they might dig up fossils (traces of ancient organisms) that will solve some of the mysteries surrounding dinosaurs and how they lived.

The chances of finding fossils are good: "Liaoning is one of the most important fossil areas in the world," says Mark Norell, a paleontologist who studies fossils at the American Museum of Natural History in New York. Just last October, Norell and his colleague Xu Xing announced that fossil hunters had unearthed a 2 meter (6.5 foot)-long feathered tyrannosaur--in the same family as the towering, toothy T. rex--in the area.

After studying this fossil, Norell and Xu concluded that the ostrich-size dinosaur had been cloaked in downy feathers from head to tail. Their discovery rocked the scientific community. Why? It was the first evidence that tyrannosaurs, relatives of today's birds, had a feathery covering.

Liaoning's fossil beds--formed when sediments were compacted and cemented together--have revealed other surprises too. Armed with shovels and picks, fossil hunters have dug 50-feet-deep holes to find thousands of plant and animal remains. With these fossils, paleontologists have pieced together an ancient forest ecosystem called the Jehol (JEE-hole) Forest. Science World spoke with Norell to learn more.

What makes Liaoning Province so unique?

It is probably the most accurate picture of an ancient ecosystem. Most of the time when you find fossils, you find only the remains of large animals. But Liaoning has provided us with a fantastically diverse fossil record that includes fossils of plants and invertebrates [animals without a backbone] such as crayfish, dragonflies, and fly-like creatures. It is rare to find so many different types of animals from the same time period buried together.

When you studied these fossils, did you find anything surprising about the Jehol Forest?

If you think about the time when ancient dinosaurs lived, most people imagine a swampy scene full of gigantic, scaly animals. But in Liaoning this wasn't the case. Fossils show that the Jehol Forest looked like a modern forest with really familiar things--like dragonflies, ginkgo trees, and even pine trees. However, it also held surprises: A lot of dinosaurs would have looked really strange because they were completely feathered--like the recently discovered tyrannosaur, which we named Dilong paradoxus, meaning "surprising emperor dragon." It wasn't the first feathered dinosaur discovered, but it was the first tyrannosaur ever found with primitive feathers.

Do these fossils hold any other detailed clues about the animals--such as their color?

In Liaoning, many of the fossils preserved soft tissue. Sometimes, this allows us to tell if an animal was patterned because we can see spots and stripes. What colors were those spots and stripes when the animals were alive? We don't know.

How are fossils created?

There are lots of kinds of fossils--and each one forms in a different way. When most people think of fossils, they think of replacement fossils. Replacement fossils form when common minerals, such as silica and calcite, replace an organism's bones or other body structures (see Nuts & Bolts, p. 15). Another fossil type is an imprint fossil, which includes molds (impressions of bones in rock) or trace fossils such as footprints.