“Tylosaurs are already notorious for being one of the largest-sized mosasaurs that ever lived,” says Tiago Simões, an evolutionary biologist at Princeton University. “I think this study further supports that, making them the largest group of mosasaurs that ever lived.”
In addition to describing the new species, Zietlow and her team also assembled a comprehensive dataset on mosasaur anatomy, updating the older, rickety version from scratch with head-to-tail measurements of 300 mosasaur specimens and modern lizards
“I hope people are able to use it and give tylosaurs the attention I don’t think they’ve had,” says Zietlow.
Measuring sea monsters
The first known Tylosaurus species, T. proriger (“prow-bearing knob lizard”), was named 150 years ago for the battering-ram-like tips of its jaws. At around 30 feet long, “it was the largest North American mosasaur known for quite some time,” says Mike Polcyn, a vertebrate paleontologist at Southern Methodist University and an author on the study. “Because the snout was so easily recognizable, people could differentiate it easily from other mosasaurs.”
While paleontologists have described other species of Tylosaurus over the years, most of the specimens found in the 84-million-year-old rocks of Kansas are assigned to T. proriger. By custom, several giant specimens originally found in the 80-million-year-old rocks around Dallas, Texas, including a large one now mounted at the Perot Museum of Nature and Science, were also given this classification.