Jaws of death: Paleontologist renames giant, prehistoric marine lizard


Date:
September 23, 2020
Source:
Utah State University
Summary:
Paleontologists describe a new genus of mosasaur, Gnathomortis
stadtmani, a marine lizard that roamed the oceans of North America
toward the end of the Age of Dinosaurs.



FULL STORY ==========================================================================
Some 92 to 66 million years ago, as the Age of Dinosaurs waned, giant
marine lizards called mosasaurs roamed an ocean that covered North America
from Utah to Missouri and Texas to the Yukon. The air-breathing predators
were streamlined swimmers that devoured almost everything in their path, including fish, turtles, clams and even smaller mosasaurs.


========================================================================== Coloradoan Gary Thompson discovered mosasaur bones near the Delta County
town of Cedaredge in 1975, which the teen reported to his high school
science teacher. The specimens made their way to Utah's Brigham Young University, where, in 1999, the creature that left the fossils was named Prognathodon stadtmani.

"I first learned of this discovery while doing background research for my Ph.D.," says newly arrived Utah State University Eastern paleontologist
Joshua Lively, who recently took the reins as curator of the Price campus' Prehistoric Museum. "Ultimately, parts of this fossil, which were prepared since the original description in 1999, were important enough to become
a chapter in my 2019 doctoral dissertation." Upon detailed research of
the mosasaur's skeleton and a phylogenetic analysis, Lively determined
the BYU specimen is not closely related to other species of the genus Prognathodon and needed to be renamed. He reclassified the mosasaur as Gnathomortis stadtmani and reports his findings in the most recent issue
of the Journal of Vertebrate Paleontology.

His research was funded by the Geological Society of America, the Evolving Earth Foundation, the Texas Academy of Science and the Jackson School
of Geosciences at The University of Texas at Austin.

"The new name is derived from Greek and Latin words for 'jaws of
death,'" Lively says. "It was inspired by the incredibly large jaws
of this specimen, which measure four feet (1.2 meters) in length."
An interesting feature of Gnathomortis' mandibles, he says, is a large depression on their outer surface, similar to that seen in modern lizards,
such as the Collared Lizard. The feature is indicative of large jaw
muscles that equipped the marine reptile with a formidable biteforce.

"What sets this animal apart from other mosasaurs are features of the
quadrate -- a bone in the jaw joint that also forms a portion of the ear canal," says Lively, who returned to the fossil's Colorado discovery
site and determined the age interval of rock, in which the specimen
was preserved.

"In Gnathomortis, this bone exhibits a suite of characteristics that
are transitional from earlier mosasaurs, like Clidastes, and later
mosasaurs, like Prognathodon. We now know Gnathomortis swam in the seas
of Colorado between 79 and 81 million years ago, or at least 3.5 million
years before any species of Prognathodon." He says fossil enthusiasts
can view Gnathomortis' big bite at the BYU Museum of Paleontology in
Provo, Utah, and see a cast of the skull at the Pioneer Town Museum in Cedaredge, Colorado. 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.

"I'm excited to share this story, which represents years of effort by
many citizen scientists and scholars, as I kick off my new position at
USU Eastern's Prehistoric Museum," Lively says. "It's a reminder of the
power of curiosity and exploration by people of all ages and backgrounds."

========================================================================== Story Source: Materials provided by Utah_State_University. Original
written by Mary-Ann Muffoletto. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Joshua R. Lively. Redescription and phylogenetic assessment of
`Prognathodon' stadtmani: implications for Globidensini monophyly
and character homology in Mosasaurinae. Journal of Vertebrate
Paleontology, 2020; e1784183 DOI: 10.1080/02724634.2020.1784183 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200923090424.htm

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