Largest Tyrannosaur Fossil Unearthed In Montana

September 16, 1997

A fossilized skeleton believed to be the largest specimen of a Tyrannosaur ever unearthed was found this summer by a field crew headed by J. Keith Rigby, a University of Notre Dame paleontologist. The fossil, which has been only partially excavated, lies in a vast dinosaur graveyard in northeastern Montana near the Fort Peck Reservoir.

According to Rigby, the fossil is nearly complete and is either a Tyrannosaurus rex or something very much like it. Certain aspects of the anatomy are different than the 15 or so known skeletons of T. rex, he says, and it appears to exceed all measured skeletons of the dinosaur. "What we do know is that it's the largest carnivore on the planet.," he says.

Rigby reports that the pubis, one of three main bones in the pelvis, measures at least 52 inches, compared to 48 inches in the largest known T. rex. The femurs or thigh bones, which paleontologists normally use to estimate the size of dinosaurs, await excavation at the site.

Unfortunately, former owners of the cattle ranch on which the fossils were found entered the site and began digging up the bones that remained in the ground, including the skull. Contending they still own the land, they evidently planned to sell the fossil to a private collector.

On Sunday (Sept. 14), Federal law-enforcement officers descended on the site, which a title search indicates lies on land now owned by the U.S. Dept. of Agriculture's Farm Service Agency, and forced the former owners to vacate the premises.

Rigby and the Earthwatch Institute, which funded a major part of the research, had planned to complete the excavation and receive independent corroboration of the fossils before jointly announcing the discovery, but the events unfolding on the site have forced their hand. Rigby had temporarily closed the site in August and returned to Notre Dame to begin the fall semester.

He is likely to visit the site soon to assess the damage done in his absence.

Situated in the picturesque badlands of eastern Montana, the site lies in the Hell Creek, a geological formation famous for preserving dinosaur bones. The bones date from the end of the Cretaceous period 66 million years ago. In the Late Cretaceous, the now bone-dry site sppears to have been a river channel, according to Rigby. When the dinosaurs died, their bones washed into the channel and collected together there. Sediments covered and preserved the bones until they were discovered in July by the Notre Dame/Earthwatch team.

Rigby credits four Earthwatch volunteers for playing a critical role in the discovery. Carol Schuler of Brooklyn, N.Y., and Rhonda King of Hollidaysburg, Pa., were the volunteers who located the fossil bed rich in dinosaur remains and unique because of the diversity represented. And Steve Begin, a forestry consultant from Manistee, Mich., and Louis Trembley, an earth science teach from Avon High School in Avon, Conn., found the large Tyrannosaur. According to Rigby, Trembly drew the group's attention to the site by literally stumbling overa protruding bone.

Judging from the position of both surface bones and the bones so far unearthed, Rigby believes the bone bed may cover 15 acres, making it one of the largest dinosaur graveyards of the Late Cretaceous ever found.

"All of these discoveries await complete excavation of the fossils and rigorous scientific analysis, including independent corroboration," says Rigby.

Rigby plans to donate the fossils to a proposed museum in Fort Peck, Mont., tentatively known as the Fort Peck Dam Interpretive Center and Museum. Slated to open in 2005, the museum as currently conceived will feature the largest dinosaur exhibit in the world. "Rigby's donation will be a major contribution to a world-class museum," says Larry Mires, who heads the museum effort.

Earthwatch is a nonprofit organization that funds more than 130 scientific field research projects worldwide every year. Since it was founded in 1972, more than 50,000 paying volunteers -- 4,000 each year -- have shared the cost and labor of the expeditions, which investigate questions in the earth, life, and social sciences.

"We are concerned that the fossils be properly excavated and prepared for placement in the museum for the benefit of the general public," says Roger Bergen, president of Earthwatch.

Rigby has received Earthwatch support for field research for the past nine years and a total of 420 Earthwatch volunteers have worked on his field crews.

Rigby can be reached in his office at (219) 631-6245. For Earthwatch information, contact Blue Magruder or Peter Tyson at Earthwatch at (617) 926-8200.
-end-


University of Notre Dame

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