Gnathomortis stadtmani , the only species in the newly described mosasaur genus, swam in the seas of North America between 79 and 81 million years ago (during the Cretaceous period). The skull and a partial skeleton of Gnathomortis stadtmani were discovered in western Colorado in 1975 and in 1999 it was initially assigned to the genus Prognathodon as Prognathodon stadtmani.
Now, in a new study published in the Journal of Vertebrate Paleontology, paleontologist Joshua Lively of the Jackson School of Geosciences at the University of Texas at Austin (USA) describes how he examined the original specimen and the recently discovered remains of the upper area of the skull, jaw and brain box of the mosasaur, determining that the fossils are not closely related to other species of the genus Prognathodon and need to be renamed.
“The new name, Gnathomortis , is derived from the Greek and Latin words for ‘jaws of death, ‘” says Lively. “It was inspired by the incredibly large jaws of this species, which are 1.2 meters long .”
Mosasaurs comprise a group of large marine reptiles that contain a total of 38 genera. According to Lively, what distinguishes this animal from other mosasaurs is the presence of a bone in the jaw joint which, in turn, forms a part of the ear canal.
“In the Gnathomorti s, this bone exhibits a set of characteristics that are transitional from earlier mosasaurs, such as Clidastes, and later mosasaurs, such as Prognathodon. Now we know that 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 ”, comments the scientist.
In addition, an interesting feature of the mosasaur’s jaws is a large depression on its outer surface, similar to that seen in modern lizards, such as the collared lizard ( Crotaphytus collaris ) that inhabits the southern United States and the north. from Mexico. It is indicative of the large jaw muscles that equipped this prehistoric, gigantic marine reptile with formidable bite force.
Mosasaurs swam through an ocean that covered from Utah to Missouri and from Texas to the Yukon 92 to 66 million years ago. These predators peaked as the age of dinosaurs was drawing to a close, devouring a wide range of prey, from clams and turtles to even smaller mosasaurs. And it is that during the last 20 million years of this period, mosasaurs became the dominant marine predators after the extinction of ichthyosaurs and pliosaurs. They became extinct due to the Cretaceous-Paleogene or Cretaceous-Tertiary mass extinction event (K-Pg event) of the late to late Cretaceous period.
“We now know that Gnathomortis swam in the seas of Colorado between 79 and 81 million years ago, or at least 3.5 million years before any Prognathodon species.”
Where to see this prehistoric giant?
His remains can be seen at the BYU Museum of Paleontology in Provo, Utah (United States).
Referencia: Joshua R. Lively. Redescription and phylogenetic assessment of ‘Prognathodon’ stadtmani: implications for Globidensini monophyly and character homology in Mosasaurinae. Journal of Vertebrate Paleontology, published online September 23, 2020; doi: 10.1080/02724634.2020.1784183
