Texas now has its own T. rex that ruled the Cretaceous seas with an iron jaw.
Researchers have identified a previously unknown species of giant mosasaur, a fearsome marine reptile that once prowled the ancient seas. And in a fitting nod to its sheer dominance, scientists named it Tylosaurus rex — meaning “king of the tylosaurs.”
Published in the Bulletin of the American Museum of Natural History, the discovery does more than just add a new gargantuan predator to the fossil record. It is also changing how paleontologists study mosasaur evolution, thanks to an update to a scientific dataset that has remained largely the same for decades.
“These are living, breathing animals. They weren’t movie monsters. They lived, they died, they bled, they ate, they tried not to be eaten, they tried to make more of themselves,” Ron Tykoski, one of the study authors, told Discover. “And so a discovery like this really does just give us these faintest glimpses, these little snapshots of life in the past.”
How Scientists Discovered Tylosaurus rex
Teeth of Tylosaurus rex specimen PMNS 2021-03-01
(Image Courtesy of PerotMuseum of Nature and Science)
Sometimes, scientific breakthroughs begin with something that looks just a little off.
In this case, lead study author Amelia Zietlow was examining fossils in a research collection when she stumbled upon a mosasaur specimen that appeared to be mislabeled as Tylosaurus proriger. After comparing the fossil to the original T. proringer holotype, the team started to suspect they were looking at something entirely different.
The fossils were significantly larger than those of T. proriger and had finely serrated teeth. Additionally, while T. proriger fossils are typically found in what is now Kansas and date to around 84 million years ago, these specimens were mostly found in northern Texas and are roughly 80 million years old.
Soon, researchers realized they weren’t dealing with a single unusual fossil, as more than a dozen previously discovered specimens appeared to belong to the same giant species.
Read More: Fossils May Reveal a Clash of the Titans Between Two Undersea Reptiles
What Makes Tylosaurus rex Different From Other Mosasaurs?
At up to 43 feet long, Tylosaurus rex rivaled the size of a school bus, measuring roughly twice the length of the largest great white shark. But size alone wasn’t what made this sea reptile stand out.
Researchers found evidence that T. rex possessed an especially powerful jaw and neck muscles, suggesting it was built to overpower prey with tremendous force. Its finely serrated teeth likely made it particularly effective at slicing through flesh.
“They’re taking larger prey, they’re flipping their head up, gaping wider and slamming teeth down harder. And then... the design of having these micro-serrations along the tooth edge, just like a steak knife. Why do you have little bumps on a steak knife instead of a smooth edge? Well, because it helps saw through meat better. Same thing in nature,” said Tykoski to Discover.
The team also uncovered evidence of injuries within the species that suggest a level of aggression rarely seen in other Tylosaurus fossils. One specimen nicknamed “The Black Knight,” housed at the Perot Museum, is missing the tip of its snout and sports a fractured lower jaw. Researchers believe the injuries were likely inflicted by another member of its own species, hinting at brutal clashes between these prehistoric giants.
“You see the injuries on this individual, and the only other organism around in this place at this time that could have inflicted those is another one of its own species. That just had to be an incredibly violent interaction between these animals. They evidently didn’t like each other, or were very territorial, or maybe they were cannibalistic. We don’t know the exact ‘why,” Tykoski told Discover.
Why a New Mosasaur Dataset Matters
Right upper jaw of Tylosaurus rex specimen PMNS 2021-03-01.
(Image Courtesy of Perot Museum of Nature and Science)
For nearly 30 years, researchers studying mosasaur evolution have relied on essentially the same dataset to understand how different species are related. As part of the new study, scientists comprehensively revised that framework and proposed a new evolutionary arrangement for tylosaurs.
Just as importantly, the research reinforces Texas as a fossil hotspot for understanding ancient marine ecosystems. And with a refreshed dataset now in hand, paleontologists and amateur fossil hunters can enter a new chapter in unraveling the mosasaur’s evolutionary story.
“I could get a call any day now that says, ‘Hey, I found some more bones.’ The great thing is that the scientific method operates by disproving, by testing, and falsifying. So, if somebody doesn’t like what they see, excellent! Tell us we’re wrong. That’s how science advances,” concluded Tykoski.
Read More: Did This Giant Sea Lizard Rule the Oceans 66 Million Years Ago?
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article references information from a study published in the Bulletin of the American Museum of Natural History: A gigantic new species of Tylosaurus (Squamata, Mosasauridae) from Texas : and a revised character list for phylogenetic analyses of Mosasauridae (Bulletin of the American Museum of Natural History, no. 482)
