Crushed bones reveal literal dino stomping ground

October 14, 2009
The diagonal fracture in the ischium bone of a Venenosaurus suggests the break occurred when the bone was still fresh. Credit: Brooks Britt / BYU

Imagine the gruesome sound of bones snapping as a thirsty, 30-ton dinosaur tramples a heap of fresh carcasses on his way to a rapidly shrinking lake.

That's the scene revealed by a painstaking analysis of thousands of bones unearthed near Moab, Utah by geologists from Brigham Young University.

So far the researchers have identified 67 individual dinosaurs representing 8 species - and they have only scratched the surface of this diverse quarry. Mysteriously, nearly all of the 4,200 bones recovered so far are fractured, as reported in the scientific journal Palaeo.

"Although enough bones were recovered to assemble several complete dinosaurs, the vast majority of bones are broken to bits and pieces, just pulverized," said BYU professor Brooks Britt, lead author on the study.

The researchers reconstructed how the bones got there and why they are in such bad shape.

The quarry, located immediately west of Arches National Park, contains dinosaurs of all sizes and ages, indicating a massive die-off event. The location of this dense cluster of bones - near the shore of an ancient lake bed - suggests a drought was the cause.

Yet the biggest puzzle was the cause of all the fractures. A closer look revealed that most of the breaks were angled "greenstick" fractures that occur in fresh bones.

The bones broke before they became brittle.

"Some of these bones were almost 5 feet long, and they are green, and you really have to work hard to shatter that's still green," Britt said. "That means the big boys were stepping on those things. Those would have been audible, big snaps."

The heavy-footed culprits? Huge, plant-eating sauropods and iguanodontids that stomped more than 100 million years ago during the Early . Some of the sauropods from this quarry are cousins to the brachiosaurus.

The bones are now housed in BYU's Earth Science Museum, which will re-emerge as the Museum of during Homecoming weekend.

Museum curator Rod Scheetz, a co-author on the study, says the grand re-opening will include the debut of a 9-foot-long triceratops skull from Montana.

Source: Brigham Young University (news : web)

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not rated yet Oct 14, 2009
Can someone explain to me how a 30 ton dinosaur which would require lots more water consumption could out last smaller dinosaurs? Seems drought is not a very good explanation. The 30 tons should've died out first?
not rated yet Oct 14, 2009
Can someone explain to me how a 30 ton dinosaur which would require lots more water consumption could out last smaller dinosaurs? Seems drought is not a very good explanation. The 30 tons should've died out first?

While I'm certainly no expert in these areas I would think that an assumption could possibly be made on the basis of a modern analogy - in a similar severe drought or desertification event today, a camel would (I presume) last longer than a horse or goat. Conversely elephants, as I understand it, need to drink daily so perhaps a horse would outlast them.

I don't think the metabolism of dinosaurs is known or inferred with enough accuracy to be exact about which species should do better in such conditions but maybe an expert in this can provide more detail?
not rated yet Oct 14, 2009
Also, it could be suggested they outlasted because they were able to trample the smaller species into oblivion while racing to the remaining pockets of water :P
not rated yet Oct 14, 2009
I wonder if it was some bizarre behavioral trait that caused some dinosaurs to trample the dead or dying.
not rated yet Oct 14, 2009
Large animals might do better in a drought -- their surface to volume is smaller than small animals.
not rated yet Oct 15, 2009
That means the big boys were stepping on those things.
Case closed? Geez. My advisor would never let me get away with such a definitive statement. Let's all just stop thinking, shall we?
not rated yet Oct 15, 2009
Well if its a drought though, its not an immediate loss of water necessarily. Your plants would also die off would they not? So the whole herbivore food source is going, and you have 30 ton dinos that need more food and water on average. I thought about camels, but I dont know if thats consistant with a 30 ton dino. It would seem though its at least the cause of some stampede, more so than the result of a drought. Running from or to something, that would cause them not to care who they stepped on, as most animals dont purposely trample, that I'm aware of.

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