Enormous Ancient "Jaws Of Death" Marine Reptile Described For The First Time


Rachael Funnell

Social Editor and Staff Writer

clockSep 23 2020, 08:15 UTC

A cast of the newly-described mosasaur Gnathomortis stadtmani's bones mounted at Brigham Young University. Joshua Lively/BYU

Closer analysis of fossils found in 1975 has revealed a new genus of mosasaur, a group of ancient, reptilian ocean giants. Named in honor of their enormous jaws, the given genus translates to “jaws of death”, which seems all too fitting for a marine predator with a mouth 1.2 meters (4 feet) in width. Published in the Journal of Vertebrate Paleontology, this new research is said to be the product of years of effort from citizen scientists and scholars alike, demonstrating how anyone can be pivotal in rewriting our planet’s past.

Mosasaurs swam through an ocean that covered from Utah to Missouri and Texas to the Yukon 92 to 66 million years ago. The air-breathing predators reached their peak as The Age of Dinosaurs was coming to its natural end, devouring a diverse range of prey including anything from clams and turtles to smaller mosasaurs.


The bones in question were first discovered by a teenager who reported his find to a high school science teacher. They made their way to Utah's Brigham Young University where they were later identified as belonging to the mosasaur species Prognathodon stadtmani.

The reptilian predator was certainly an ocean giant. Joshua Lively/BYU

The ID is now being challenged by Utah State University Eastern paleontologist Joshua Lively, who recently took over as curator of the Price campus' Prehistoric Museum. Lively investigated the mosasaur's skeleton and carried out a phylogenetic analysis before landing at the conclusion that the specimen needed to be renamed, reclassifying it as Gnathomortis stadtmani, which is derived from the Greek and Latin words for "jaws of death".

And jaws of death they were indeed, as an interesting depression on the outer surface of Gnathomorits’ mandibles indicate they functioned similarly to those belonging to the extant collared lizard. This implies they could close their more-than-a-meter-long jaws with a formidable bite force.

Depressions on its mandibles likely meant Gnathomorits had a bite force beyond that of even larger mosasaur species. Joshua Lively/BYU

“Through its life, Gnathomorits would have competed with large bony fish, sharks, and other mosasaurs for resources in its environment,” Lively told IFLScience. “When it reached adult size, its main competition would have probably been the mosasaur Tylosaurus, which lived at the same time in the Western Interior Seaway and reached even larger sizes than Gnathomortis stadtmani. Gnathomortis is interesting because it is the first member of its particular mosasaur lineage (the Mosasaurinae) to evolve a skull length of greater than 1 meter… That probably translated to a total body length of 9 or 10 meters!

“This mosasaur was discovered by a kid named Gary Thompson in 1975. Forty-five years later, I am excited to shed new light on Gary's discovery and highlight how everyone can make important contributions to the scientific process.”