Ancient Ocean Predators Re-Classified By USU Eastern Museum Curator

Oct 6, 2020

BYU's Eyring Science Center features a skeletal mount of the mosasaur "Gnathomortis stadtmani'. Paleontologist Josh Lively of USU Eastern named the huge marine reptile that dominated the Western Interior Seaway of North America near the end of the Age of Dinosaurs.
Credit BYU

Almost 50 years after it’s discovery, a gigantic prehistoric reptile has recently been re-classified by the new curator of paleontology at the USU Eastern Prehistoric Museum. 

Mosasaurs are gigantic prehistoric reptiles that dominated the shallow oceans near the end of the age of dinosaurs. One specimen originally found in 1975 in Colorado by a high school student, has since been housed at Brigham Young University, where it was classified as Prognathodon stadtmani in 1999. A few years ago Josh Lively, the paleontology curator at the USU Eastern Museum studied recently prepared bones from the specimen’s jaw as part of his research.

“When you look at the Mosasaurs, how diverse they got, and how big some of them got you know, they're really coming to dominate the oceans at that time," Lively said. "So my main question then was trying to understand are there any interplays between their evolutionary history and changes within the earth system?”

When it comes to classifying mosasaurs, Lively said the part of the jawbone that also forms part of the ear canal may be the most important bone. Through his studies, he reclassified the BYU specimen Gnathomortis stadtmani-- a name that means “jaws of death.”

To place this specimen in time, he visited the site where the fossil was discovered.

“So it comes from a unit called the Mancos shale, which, in western Colorado, where it was discovered, is about 1200 meters of mud that spans about over 15 million years of time," he said.

Lively said detailed geologic mapping to study hazards anchored the time that Gnathomortis preyed on other marine life at 81-79 million years ago – several million years before Prognathodon species even existed.

Gnathomortis’ big bite can be viewed at the BYU Museum of Paleontology in Provo, Utah.  A cast of the skull can be seen at the Pioneer Town Museum in Cedaredge, Colorado. And reconstructions of the full skeleton are on display at the John Wesley Powell River History Museum in Green River, Utah, and in BYU’s Eyring Science Center.