In a remarkable discovery, paleontologists have identified a new species of giant marine reptile that once ruled the ancient seas of Texas. This apex predator, now known as Tylosaurus Rexis shedding light on the rich prehistoric biodiversity of the region.
The journey to this discovery began with a single fossil that caught the attention of Amelia Zietlowa museum specialist at the Museum at the Castle in Appleton, Wisconsin, and a recent Ph.D. student at the American Museum of Natural History. Her findings, published in the Bulletin of the American Museum of Natural Sciencehave unveiled a creature that once dominated the shallow, tropical inland sea that covered most of Texas about 80 million years ago.
The Discovery of Tylosaurus Rex
Zietlow’s curiosity was piqued in late 2026 when she encountered a fossil in the collections of the American Museum of Natural History that seemed different from others of its kind. The fossil, originating from Texas, exhibited unusual characteristics, particularly in its serrated teeth—a feature not typically seen in mosasaurs.
Collaborating with coauthors Michael J. Polcyn and Ronald S. Tykoskiboth based in Dallas, Zietlow reviewed specimens from museums across North America and Europe. Their combined efforts led to the identification of a new species, Tylosaurus Rexor T. rex for short. This species was significantly larger than previously known Tylosaurus, averaging between 30 to 35 feet in length, with the largest specimen measuring an impressive 43 feet.
The Role of Avocational Paleontologists
The discovery of Tylosaurus Rex was made possible not only by professional researchers but also by avocational paleontologists—enthusiasts who often find fossils on their own land and donate them to museums. Zietlow highlighted the crucial role these hobbyists played in her research.
“A lot of those mosasaurs were found by avocational paleontologists,” Zietlow explained. “People who were just going out in their backyards in some cases and finding these guys on their land. They then dug them up, sometimes with the museums, and chose to then donate them to those museums so that they could be studied by researchers like me.”
These specimens, housed in institutions such as Southern Methodist University and the Perot Museumprovided invaluable data for Zietlow and her team. The collaborative efforts of hobbyists and researchers were instrumental in uncovering the secrets of this ancient marine predator.
Life and Times of Tylosaurus Rex
Tylosaurus Rex, despite its name, was not a dinosaur but a giant marine reptile. Zietlow described it as resembling a Komodo dragonscaled up to the size of a school bus, with flippers, a shark’s tail, and an extra row of teeth on the top of its mouth.
As a generalist predator, Tylosaurus Rex would have attacked almost anything that swam past, using its knife-like teeth to hunt ancient fish and other marine reptiles, such as the long-necked plesiosaur. The brutal nature of its life is evident in a fossil at the Perot Museum, nicknamed the “Black Knight” after the Monty Python character, which is covered in severe bite marks.
This discovery has not only identified a new species but also shed light on the overall diversity and evolutionary patterns of mosasaurs. Zietlow and her team are now looking into other mosasaurs from across Texas, a region rich in prehistoric marine life.
