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Mosasaur: Died in Cretaceous Period, Found in 1975, Displayed in 2017

Back in his day, Craig Slover walked to school—and found the fossil remains of a thirty-foot-long mosasaur.

A cast of the fossil now hangs from the ceiling of the Eyring Science Center. Dr. Rod Scheetz, curator of the BYU Museum of Paleontology, said the fossil’s jaw shows definite scarring—evidence of violent interactions with other mosasaurs.

Those scarred jaw bones were found one day in 1975. Fourteen-year-old Slover first noticed the skeleton as he walked three miles to school in Cedaredge, Colorado.

Scheetz said that the mosasaur’s carcass had been buried at the bottom of the sea in sediments now known as Mancos Shale, and after millions of years of erosion, the fossils were finally exposed in the hillside overlooking Cedaredge.

At first, it looked to Slover like they might just be random rocks sticking out of the bank. Upon closer inspection, he noticed the unusual pattern of the rocks, and he started to think that they had to be something else.

“I stopped and took a better look and thought, ‘These don’t really look like rocks,’” Slover said.

In want of another opinion, Slover brought back his two best friends to the site, and the group all decided the rocks definitely weren’t ordinary rocks. The boys raced back to school and notified their science teacher, Bob Eklund, of the discovery.

“Mr. Eklund got very excited, and he loaded us up in his car and drove us all back up there,” Slover said. “And after inspecting the strange formation of the bones, he officially declared that I had found a dinosaur.”

But it wasn’t exactly a dinosaur; it was a mosasaur. Mosasaurs are large marine reptiles that lived during the Cretaceous period. Scheetz said the monstrous reptile reigned in the waters about 82 million years ago when the Western Interior Seaway covered Colorado and most of Utah.

Scheetz explained that shortly after Slover found the mosasaur, Dr. James Jensen was called to collect the fossil. Jensen was known as Dinosaur Jim, and the BYU Museum of Paleontology was first built around fossils he collected.

The fossil remains found at the site included the skull of the mosasaur—sleek, long, and racked with large teeth—around a dozen vertebrae, several ribs, and a partial flipper, according to Scheetz.

Slover said the recovery process caused quite a buzz among the locals, and even people outside the county came by the busload to see the fossil remains.

“This made it difficult for us to get up the mesa to get home where we lived, but at the same time, it was very exciting,” Slover said.

The mosasaur has been part of BYU’s collection ever since, and you can now view it in the Eyring Science Center.

Mosasaur display installation time lapse video.

By Jessica Parcell Posted on