The secret life of dinos: step back in time with the largest beasts ever to walk the Earth - Earth/Life Science: Cretaceous Period Dinosaurs Fossils.Tyrannosaurus rex fossil discovery - Statistical Data Included

Science World, Oct 15, 2001 by Kim Masibay

FOSSIL SCIENCE

When Hendrickson unearthed her find, she knew she was looking at a Late Cretaceous fossil. "You can tell a fossil's age by the layer of earth in which it's deposited. Give or take a million years," she says. (see diagram pp. 14-15).

Rock layers are windows into specific time periods. Poke around in 65-million-year-old sedimentary rock and you might find a T. rex. Fossils form only where sand or mud quickly buried carcasses: in deserts, floodplains, or debris-clogged riverbeds. When T. rex lived, the Hell Creek Formation was floodplain, webbed with rivers. But millions of years of erosion exposed Sue's bones.

Dinos may have roamed the entire Earth, but just as giraffes are indigenous (native) to Africa, scientists think T. rex evolved and lived only in what is now western North America.

REBUILDING SUE

For three weeks, Susan and the team move dirt and wrap bones in foil and plaster casts. "What's important is keeping every little piece," says Hendrickson.

As they move the massive but fragile bones encased in matrix (non-fossil rock that surrounds bone) into trailers for transport, the number of bones stuns them: with more than 250 bones, the skeleton is 90 percent complete--the most complete T. rex ever found!

In May 2000, all 14,000 pounds of beautiful, chocolate-colored bones are finally assembled on a custom iron frame, now on display at Chicago's Field Museum of Natural History. "I worried Sue wouldn't live up to expectations," Hendrickson says. "But she didn't let us down. I still get chills when I see her."

NOSE JOB The T. rex snouts you've seen in Jurassic Park III, The Lost World, or Disney's Dinosaur may be all wrong. New research suggests that dino nostrils belong down near the mouth. "It may appear dramatic in the movies," says biologist Lawrence Witmer of the DinoNose project at Ohio University in Athens, but he proposes a new T. rex nose design, with which many scientists agree.

Flesh isn't preserved in fossils, and a T. rex nostril could have been located anywhere along the skull's bony nasal openings. In dinos' closest living relatives, birds and crocodiles, the nostril sits at the front of the bony nostril. Also, blood vessels that feed nasal tissue leave distinct marks on the skull bones of modern crocodiles--Witmer found similar markings on dino skulls. That's nothing to sneeze at!

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Geological Time

Geologists know about ancient life from fossilized remains of creatures buried in layer upon layer of rocks or sediment. The geological time chart reveals the layers and the sequence of fossil history.

Precambrian Era: Earth formed. The first single-celled life forms appeared 3.6 billion years ago (bya). Continents took shape about 3 bya.

Paleozoic Era: Algae and other boneless life forms filled the oceans. Crustaceans and fishlike animals appeared. Simple plants grew on land, then giant ferns, and later vast conifer forests. By 290 million years ago (mya), reptiles evolved.

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Mesozoic Era: In the Jurassic Period dinosaurs and the first birds evolved. By the Cretaceous Period, small mammals appeared, and T. rex ruled North America. Dinosaurs died out at the end of the Mesozoic Era.