Paleontologists have described a new species of mosasaur, Tylosaurus rex, based on fossils collected from 80-million-year-old rock formations near Dallas, Texas. The species is among the largest known mosasaurs. The findings were published in the Bulletin of the American Museum of Natural History.
Discovery and Classification
The type specimen for Tylosaurus rex was discovered in 1979 in Texas and is housed at the Perot Museum of Nature and Science. The species belongs to the genus Tylosaurus, a group of extinct marine reptiles known as mosasaurs.
Researchers analyzed over a dozen large specimens from several museums and compared them with 130 modern lizard species. Based on this analysis, the specimens were reclassified as a new species, distinct from the previously known Tylosaurus proriger. A total of 12 specimens have been reclassified as T. rex, including the specimens known as "Black Knight" (Perot Museum), "Bunker" (University of Kansas), and "Sophie" (Yale Peabody Museum).
Physical Characteristics
Size and Scale: Tylosaurus rex specimens range from 25 to 43 feet (approximately 7.6 to 13.2 meters) in length, dwarfing the previously known T. proriger which typically reached about 30 feet.
Distinctive features of T. rex include:
- Finely serrated teeth
- Differences in the skull, jaw, and mouth relative to other Tylosaurus species
- Skull and neck anatomy associated with a powerful bite
Temporal and Geographic Distribution
The species lived during the Late Cretaceous period, approximately 80 million years ago. Most true T. proriger specimens date to about 84 million years ago and are found in Kansas. In contrast, T. rex specimens are concentrated in Texas and date to about 80 million years ago, suggesting T. rex lived approximately four million years after T. proriger. Previously, large mosasaur specimens from Texas had been classified as T. proriger.
Naming
The name Tylosaurus rex, meaning "king of the Tylosaurs," was chosen as an homage to the dinosaur Tyrannosaurus rex and a previous informal suggestion by paleontologist John Thurmond. Lead author Amelia Zietlow stated the animal's characteristics, such as its larger jaw and bite, justified the name. Co-author Mike Polcyn noted that repeated anatomical traits in the Texas specimens indicated they were not T. proriger.
Observations
Paleontologist Ron Tykoski stated that evidence of intraspecific violence was observed, suggesting the species engaged in fights with members of its own kind.
Background
The first Tylosaurus species, T. proriger, was described 150 years ago. Paleontologist Amelia Zietlow noted that the discovery highlights the need to re-examine long-standing assumptions about mosasaur evolution and update research methods.