Tylosaurus Rex Discovery in Texas

On Thursday, May 21, 2026, scientists at the American Museum of Natural History, the Perot Museum of Nature and Science, and Southern Methodist University announced the identification of the Tylosaurus Rex: a fossil the size of a school bus that once came from the seas above North Texas.

The mosasaur, a marine reptile that lived with the dinosaurs, was named Tylosaurus rex, meaning “T. rex of the sea.” This creature ranged in size from 25 to 45 feet long. It is believed to have been one of the later species of mosasaurs wiped out by the asteroid impact, 66 million years ago, according to researchers.

Tylosaurus Rex: Evolution of Discovery

The holotype was found in 1979 by a family enjoying a boat ride on Lake Ray Hubbard. Vice president of science and curator of vertebrate paleontology at the Perot, who was co-author of the study, Ron Tykoski, says, “The kids got a little antsy, started getting a little whiny, so the parents beached the boat and told their kids to get out and play on the shore.”

While the children were playing, they came to some “weird-looking” rocks and showed them to their mom. She believed the rocks looked similar to large bones and called the Dallas Museum of Natural History. Researchers rushed to the site and realized they were the bones of an ancient marine reptile. The skeleton was collected and placed on display.

In 2012, Michael Polcyn, a senior research fellow at SMU and a co-author on the study, noticed something about these bones.

“There was a groove on the rim of the quadrate that was not in any of the other species.” The quadrate is a multifunctional bone equivalent to the middle ear and is an anatomical feature used by scientists to infer relationships between species. Polcyn says it is an unusual find in a tylosaurus.

Polcyn was not the first to notice something different about these types of bones. In the late 1960s, John Thurmond was a student at SMU and theorized that the abnormally large bones might belong to a new species. He dubbed the species “Tylosaurus thalassotyrannus,” or “sea tyrant.” Decades later, Polcyn would find Thurmond’s note.

“It was serendipity. I came across that letter when I was looking for something else completely,” states Polcyn as he recounted the smile the discovery gave him, confirming the research team was moving in the right direction.

The originally classified Tylosaraus prooriger has serrated, steak knife-type teeth, a large body, and a significantly strong musculature, evidenced by enlarged attachment sites on the fossil for larger, more powerful jaw and neck muscles.

This discovery adds to what paleontologists know about “the diversity of a really, really cool group that lived during the same interval of time the dinosaurs lived.” He adds that the discovery “can provide more information on what species are related, and where in history certain adaptations in the mosasaur lineage appear,” says Barry Albright, who is a professor emeritus of earth science at the University of North Florida.

These studies help to inform future research in the field, according to Takuya Konishi, an associate professor at the University of Cincinnati. He has studied mosasaurs for more than 15 years and was not involved in this study.

T. rex specimens reveal the violent nature of the giant creatures. In 2022, a fossil found in North Texas, nicknamed “The Black Knight,” showed multiple injuries, including a fractured jaw, and a portion of its snout was missing. Tykoski reports that the only animal that could inflict that level of damage would be one from the same species.

The mosasaur showed signs of healing, indicating it survived the injuries. This fossil was not the first to have evidence of injuries from another of its kind, but it most certainly contained the most extensive injuries.

Citizen Scientist Role

Most of the North Texas species named by researchers were discovered by local collectors and amateur fossil enthusiasts walking along the creeks and in open fields. Both the holotype fossil and “The Black Knight” fossils were found by nonscientists.

Polcyn says, “We couldn’t do this without the citizen scientists that actually are out there walking the outcrops every day.”

Albright likens the role of citizen scientists in paleontology to that of amateur astronomers. “Just think about how many amateur astronomers have found comets and asteroids.”

Texas Fossil Discoveries

Texas is one of the best areas in the United States to hunt for fossils because during the Cretaceous Period, most of that area was covered by a shallow, nutrient-rich sea abundant with life.

Tykoski says, “We’ve probably got the most complete record of mosasaur evolution in one geographic area in the entire world, right here in Texas.”

The scientist reminds people that the sense of wonder created by their research of the past shows what is possible for the future, which is especially important for younger generations. “These ancient animals show us what is possible. What was possible in the past, and what could be possible in the future.”

During an interview, Tykoski gestured toward a rambunctious group of children bouncing from one exhibit to another in the Perot and said, “Look at all these people who have come here to see amazing things, to see things that are beyond their imagination, and be inspired by it. These kids – hopefully, they see something in an exhibit like this, and it triggers a lifelong desire to learn more about the world.”

Sources:

Dallas News: ‘T. rex of the sea’: D-FW researchers identify new ancient marine species
Phys.org: Ancient seas get a new T. rex as massive mosasaur emerges from Texas fossils
Smithsonian Magazine: Paleontologists Discover an Ancient Marine Reptile  They’ve Dubbed the T. Rex of the Sea, Crowning Another King of the Cretaceous

Featured Image Courtesy of Rodney’s Flickr Page – Creative Commons License