\n The freshly crowned T. rex wasn\u2019t a dinosaur but a mosasaur, a gigantic ocean apex predator that lived about 80 million years ago \u2014 a bit earlier than the dinosaur king, which lived 68 million to 66 million years ago \u2014 and measured up to 43 feet (13 meters) long. The sleuthing scientists identified the species from fossils attributed for decades to a closely related mosasaur.\n <\/p>\n
\n Like the land-dwelling T. rex (rex means king in Latin), the huge creature ruled its habitat, its sawlike teeth tearing into its prey \u2014 fish, turtles and long-necked marine reptiles called plesiosaurs \u2014 \u201creally crunching through and ripping them up,\u201d said Amelia Zietlow, a paleontologist with the History Museum at the Castle in Appleton, Wisconsin. Zietlow is lead author of a new study describing Tylosaurus rex, published May 21 in the journal Bulletin of the American Museum of Natural History<\/a>.\n <\/p>\n \n Fossils of the long-snouted swimmer were found in what\u2019s now Texas and date back about 80 million years to the latter part of the Cretaceous Period<\/a>, a time when an inland sea partly covered the North American continent. For the new study, Zietlow and her coauthors examined and reclassified fossils housed in more than a dozen institutions \u2014 specimens that had been misidentified as the species Tylosaurus proriger.\n <\/p>\n \n \u201cHere we have two T. rexes, one the king of the dinosaurs on land, the other the king of the reptiles in the water, both about the same size, 40 feet long or so, and both dominant at the top of the food chain, as the biggest carnivores in their ecosystems,\u201d said paleontologist Steve Brusatte, a professor of paleontology and evolution at Scotland\u2019s University of Edinburgh, in an email. Brusatte was not involved in the research.\n <\/p>\n \n The discovery serves as a reminder that scientific breakthroughs can come from museum collections as well as newfound fossils, and that amateur dinosaur enthusiasts also can play an important part in identifying species new to science, Zietlow noted.\n <\/p>\n \n \u201cA lot of these specimens were dug up and donated by avocational or hobbyist paleontologists in the Dallas area, so there was a lot of community involvement,\u201d she said. \u201cThis is a really great case of what paleontology can be, if everyone works together.\u201d\n <\/p>\n \n For Zietlow, Tylosaurus rex\u2019s origin story began in 2020 in New York City. She was a doctoral student in the American Museum of Natural History\u2019s Richard Gilder Graduate School, examining AMNH\u2019s mosasaur specimens.\n <\/p>\n \n \u201cMy research is focused on variation, so I wanted to get a sense of the scope of different mosasaurs that were in the collection,\u201d Zietlow said. One large T. proriger fossil unearthed in Texas during the 19th century \u2014 she nicknamed it \u201cBeefcake\u201d for its size \u2014 captured her attention.\n <\/p>\n \n \u201cI had never heard of Tylosaurus being found in Texas before,\u201d she said. \u201cTypically, they\u2019re found in Kansas and South Dakota, so that stood out to me.\u201d She connected with study coauthor Michael J. Polcyn, a mosasaur specialist and senior research fellow at Southern Methodist University in Dallas, around 2022, and suggested that the AMNH specimen might represent a different species of Tylosaurus.\n <\/p>\n \n As it happened, Polcyn had been investigating this possibility for about a decade. Peculiarities in other T. proriger fossils caught his eye around 2012, but at the time there were not enough specimens to make a strong case for a species new to science, he told CNN in an email.\n <\/p>\n \n \u201cOver the years, more specimens were discovered which started filling out the gaps in our understanding of the anatomy and natural variation of the animal,\u201d Polcyn said.\n <\/p>\n \n Still, describing a species from fossils can take years. Specimens are often incomplete or poorly preserved, and other factors can muddy the waters when it comes to connecting the dots between anatomical anomalies.\n <\/p>\n \n \u201cYou need to rule out pathologies, how animals change while growing, and other factors that may account for the differences,\u201d he added.\n <\/p>\n \n Zietlow traveled to 22 museums across North America and Europe to do comparative data collection of presumed T. proriger fossils found in northeastern Texas, \u201ctaking pictures, taking measurements, taking surface scans in some cases, and building up a dataset to be absolutely positive that we were seeing a pattern that could be attributed to a species-level difference,\u201d she said.\n <\/p>\n \n Her analysis showed that at least a dozen of those fossils displayed characteristics hinting at a novel Tylosaurus species. The Tylosaurus rex holotype \u2014 or single specimen that defines a given species \u2014 is on display at the Perot Museum of Nature and Science in Dallas. This T. rex is the most complete skeleton of the species. (Study coauthor Ronald S. Tykoski is vice president of science and curator of vertebrate paleontology at the Perot Museum.)\n <\/p>\n \n Tylosaurus rex was larger than T. proriger, measuring on average about 30 to 35 feet (9 to 11 meters) from nose to tail. The skull of the largest specimen measured more than 5.5 feet (1.7 meters) long. The marine reptile also had serrated teeth, an extra bony pocket in its skull where neck muscles attached, and heavier jaw muscles, giving it a more forceful bite.\n <\/p>\n \n Tylosaurus was previously thought to be a less diverse genus than other mosasaurs. Adding T. rex to the Tylosaurus group suggests that there is greater diversity in tylosaurs than expected.\n <\/p>\n \n \u201cTylosaurus is much more interesting and much more diverse than it\u2019s ever been given credit for,\u201d Zietlow said.\n <\/p>\n \n Illuminating the diversity of mosasaurs in general also casts the so-called age of dinosaurs in a different light, Brusatte added.\n <\/p>\n \n \u201cIt wasn\u2019t only dinosaurs that thrived and dominated during this time,\u201d he said. \u201cYes, they ruled the land, but there were other equally enormous and ferocious carnivorous reptiles stalking the seas. Tylosaurus rex would have been one of the biggest and most ferocious of these, a true terror of its time, and as scary as any shark that lives today.\u201d\n <\/p>\n \n And there are more surprises in store from the newly crowned T. rex, Polcyn said.\n <\/p>\n \n \u201cA research project always generates more questions than can be addressed in a single paper,\u201d he said. \u201cWe currently have two other projects in process with colleagues and students, directly related to Tylosaurus rex, so stay tuned for some other exciting findings.\u201d\n <\/p>\n \n Mindy Weisberger is a science writer and media producer whose work has appeared in Live Science, Scientific American and How It Works magazine. She is the author of \u201cRise of the Zombie Bugs<\/a>: The Surprising Science of Parasitic Mind-Control\u201d (Hopkins Press).\n<\/p>\n![\"A](\"https:\/\/www.newsbeep.com\/ca\/wp-content\/uploads\/2026\/05\/1c-tylosaurus-rex-reconstruction-alderon-games-path-of-titans.jpg\")
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