October 14, 2009

Scientists Uncover Trampled Dinosaur Bones In Utah

Paleontologists say a vast collection of broken dinosaur bones unearthed in southeast Utah were smashed underfoot by other dinosaurs shortly after they died, The Associated Press reported.

Scientists at Brigham Young University have spent years analyzing more than 4,000 bones from a quarry just west of Arches National Park and say the bone collection - which includes at least 67 dinosaurs representing eight species - suggests a mass-die-off, likely from drought.

BYU professor Brooks Britt, lead author of a recently published study of the bones, said after the die-offs, other plant-eating dinosaurs stomped among the carcasses as they passed through, snapping most of the bones at the site.

Britt said many of the bones would have been crushed easily under dinosaurs weighing 20 tons or more with feet larger than tires, as over 95 percent of bones studied at the site were crushed.

"Some of them were just pulverized," Britt said.

The state of Utah contains some of the best-preserved dinosaur quarries in the U.S. and is a hotbed for researchers looking for clues to ancient life.

Britt and his team analyzed the site and offer insights into the lesser-known lives of dinosaurs and other lifeforms some 124 million years ago.

He said the site is a complex mix of bones that were scattered and re-scattered in prehistoric floods and sometimes trampled more than once by other dinosaurs.

Large numbers of dinosaurs keeled over, likely during drought cycles, in an area near modern-day Moab that once was likely within sight of a receding lake, according to Britt and BYU's Earth Science Museum curator Rod Scheetz, a co-author on the study.

The experts theorize that, after they died, other dinosaurs - including long-necked sauropods and herbivores called iguanodons - tromped through, grinding the bones into the mud.

"That means the big boys were stepping on those things," Britt said. "Those would have been audible, big snaps."

For years experts have picked through the site and hauled fragments, some less than an inch, back to the lab to be pieced together.

Scientists were at first puzzled by the cause of the bone fractures. Looking closer, they found that the angled breaks were similar to breaks in fresh bones that have not yet become brittle.

Britt said thumb-sized insects also ravaged many of the specimens.

Scheetz said that even though trampled dinosaur bones have been found elsewhere, the site near Moab helps fill in gaps about the early Cretaceous period, spanning roughly 145 million to 99 million years ago.

However, only a fraction of the site near Moab has been thoroughly investigated and more work is expected.

Some of the bones are on display at BYU's museum and results from the study have been published in the journal Palaeo. Scheetz said the grand re-opening would include the debut of a 9-foot-long triceratops skull from Montana.


Image Caption: The diagonal fracture in the ischium bone of a Venenosaurus suggests the break occurred when the bone was still fresh. Credit: Brooks Britt / BYU


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