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Mystery of Macabre Mass Dinosaur Grave Unearthed

The Cleveland-Lloyd Dinosaur Quarry in central Utah is home to a paleontological mystery dating back 150 million years. The quarry was discovered in the 1920s and is home to the largest concentration of bones and fossils of Jurassic theropod dinosaurs, a suborder of bipedal carnivorous predators that include Allosaurus and Tyrannosaurus rex. The site is a veritable mass grave of these dinosaurs; over 15,000 bones have been discovered and it believed thousands more still lay in the ground.

The site contains an usually high concentration of Allosaurus fossils.

The site contains an usually high concentration of Allosaurus fossils.

Scientists still aren’t sure why so many dead dinosaurs ended up in one place, but a few theories have been proposed including a mass stranding due to thick inescapable mud or perhaps even a mass death due to drought. Curiously, however, no other animal fossils have been found at the site, which is highly unusual for such fossil-rich areas. Now, paleontologists excavating fossils at the quarry believe they might have uncovered new data that shows how the mysterious mass dinosaur burial might have occurred and why the dinosaurs’ remains aren’t accompanied by other fossils.

Researchers excavating a site at the quarry.

Researchers excavating a site at the quarry.

If you’re like me and are hoping for a dinosaur ritual gladiator pit, prepare to be disappointed. A group of researchers led by Jonathan Warnock, from the Indiana University of Pennsylvania have published their study of the Cleveland-Lloyd Quarry which proposes that the remains of the dinosaurs were washed to the site at different periods post-mortem by flooding. To reach this conclusion, the researchers analyzed the chemical compositions of several soil layers taken from the site.

A section of the quarry open for public viewing.

A section of the quarry open for public viewing.

Their data show that the dinosaur remains ‘stacked’ in layers around the same times massive floods occurred, creating the densely-packed dinosaur mass grave we have today. As this corpse-laden quagmire rotted over time, the water and soil at the site become toxic to fish and reptiles, which is why other dinosaurs didn’t gnaw on the skeletal remains and why no other animal fossils are found at the quarry. Despite the rather dry explanation for its formation, the Cleveland-Lloyd Dinosaur Quarry remains one of the most rewarding and fascinating destinations for getting a first-hand glimpse into the lives (and deaths) of the dinosaurs – and it’s open to the public.