A Blog by Brian Switek

“Pearl” the Mystery Dinosaur

Dinosaurs don’t give up their secrets easily. Even finding the prehistoric animals is a trial that relies on as much luck as skill. Fossil scraps or the tip of a bone might be the only clues a prospector sees on the surface, leaving what’s contained within the rock a total mystery. And even as paleontologists begin to excavate, the identity of a fossil and just how much there seems to be can change with the tap of an awl. And that’s only the beginning of a scientific process that aims to understand the lives of our favorite Mesozoic creatures. “Pearl”, a dinosaur found this past summer in eastern Montana, is such an example of paleontology in progress.

During an expedition with the Burpee Museum of Natural History to the roughly 66 million year old exposures of the Hell Creek Formation, museum board member Steve Simpson and one of his community college students discovered some interesting bones poking out of a hill. Burpee paleontologist Scott Williams came over to have a look, and the fossils turned out to be associated foot bones of a mid-sized theropod dinosaur. Williams initially thought that the bones could have belonged to a young Tyrannosaurus similar to the “Jane” skeleton the museum had excavated years before. But the bones turned out to be parts of a much rarer, even stranger dinosaur.

The unnamed Hell Creek Fm oviraptorosaur at the Carnegie Museum of Natural History. Photo by Brian Switek.
The unnamed Hell Creek Fm oviraptorosaur at the Carnegie Museum of Natural History. Photo by Brian Switek.

As luck would have it, University of Maryland theropod expert Thomas Holtz, Jr. arrived the day after the field discovery. From the parts that had been exposed, Holtz could tell that the dinosaur was a large caenagnathid oviraptorosaur – a beaked, slender dinosaur that looked something like a huge terrestrial parrot. In honor of his hometown, Simpson nicknamed this dinosaur “Pearl.”

Pearl isn’t the first dinosaur of her kind to be found in the Hell Creek Formation. Paleontologists previously discovered a pair of partial oviraptorosaur skeletons elsewhere in the formation. A reconstruction of this roughly ostrich-sized dinosaur is on display at the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania. This dinosaur species hasn’t been officially named yet, but the exhibited mount shows that this was a lightly-built, crested, toothless, short-tailed oviraptorosaur that ran around the same habitats as the more famous Tyrannosaurus and Triceratops.

Chances are that Pearl belonged to the same species as the oviraptorosaur displayed at the Carnegie. But, from the 40 bones recovered so far, it looks like Pearl was fifteen to twenty percent larger than the other two skeletons collected so far. If Pearl belonged to the same species, then the trio of skeletons could help paleontologists understand how these peculiar North American oviraptorosaurs changed as they grew up. Then again, there’s a possibility that Pearl could represent a different species. Such conclusions await further study.

There may even be more of Pearl to collect. The dinosaur was excavated feet first, and Williams says that his crew was discovering bones up until the last day of the field season. He’s optimistic that additional bones are still preserved at the site. Next year’s expedition will find out for sure and, hopefully, add more to Pearl the mystery dinosaur.