From 2001-2005, the research team explored three pits containing stacked skeletons of at least two different kinds of previously unknown, small theropod dinosaurs. Theropods are a group of meat-eating dinosaurs that walked on their hind legs and include Tyrannosaurus rex,as well as, much smaller creatures, popularly referred to as “raptors.”And here is how it was solved:
“None of us had ever seen anything like this before,” said Dr. David Eberth, Senior Research Scientist at the Royal Tyrrell Museum, and lead author of the article being published this week in the scientific journal PALAIOS. “In most bonebeds, remains are scattered across flat surfaces, but at these sites, skeletons were stacked one on top of another, in what appeared to be pits full of volcanic mud.”
However, by examining other geologic features in the area, the team discerned the pits were, in fact, mud-filled tracks, likely left behind by the 20-tonne sauropod dinosaur, Mamenchisaurus, whose remains were also found in the area. “Discovering that the preservation of these superb small theropod skeletons was attributable to the track-making of a giant, long-necked dinosaur was simply bizarre,” says Eberth.Mamenchisaurus was reportedly over 45 feet long and weighed over 40 000 pounds. Stomped 'em flat.
“These pits are a fantastic resource as they yield small dinosaurs that aren’t preserved well in the fossil record. Finding so many skeletons and new kinds of small theropods is already helping us clarify growth patterns and evolution in these ancient animals and their close relatives.”
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