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In a paper published on May 21 in the Bulletin of the American Museum of Natural History, three paleontologists named a 13.2-meter-long marine predator found in Texas and forgotten in museum collections for decades, misidentified as another species: now officially Tylosaurus rex, the T. rex of the seas that dominated the North American oceans 80 million years ago.
The main fossil was found in geological layers of Texas that correspond to the end of the Upper Cretaceous.
The creature lived between 81 and 79 million years ago, in the Campanian stage.
The size confirmed by measurements of the skull and cervical bones reaches 13.2 meters, or 43 feet.
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For visual comparison, it’s equivalent to two articulated buses parked in a row.
The predator reigned in the Western Interior Seaway, a gigantic shallow sea that cut through North America from north to south during the Cretaceous.
The sea covered from the Canadian Arctic to the Gulf of Mexico.
It divided the continent into two land masses: Laramidia to the west and Appalachia to the east.
The Tylosaurus rex was the top predator of this entire marine ecosystem.
I imagine the terror of swimming in that sea while the sun entered the shallow waters and illuminated a thirteen-meter gray silhouette coming towards us.
The paper is authored by Amelia R. Zietlow, Michael J. Polcyn, and Ronald S. Tykoski.
It was published on May 21 in issue 482 of the Bulletin of the American Museum of Natural History, with 77 pages and 50 figures.
The three researchers came from the American Museum of Natural History in New York, the Perot Museum of Nature and Science in Dallas, and Southern Methodist University.
The fossil that no one had identified
The unusual part of the story is that the fossil had been in museum collections for decades, misidentified as another species of mosasaur.
The previous name was Tylosaurus proriger, a related species that lived further north, in what is now Kansas, about 4 million years earlier.
A careful analysis of the jaw, skull bones, and tooth count was enough for researchers to realize it was a new, distinct species.
The differences remain even in specimens of similar body size, according to the paper.
It’s the kind of discovery that shows how paleontological collections hold secrets that gradually reveal themselves over generations of researchers.
The serrated teeth that changed history
The most striking feature of Tylosaurus rex is a rare characteristic in mosasaurs: finely serrated teeth.
They are small serrations, similar to those of a butcher’s saw, distributed along the cutting edge.
Most known mosasaurs have smooth conical teeth, optimized for piercing and holding prey.
The serrated teeth suggest cutting in motion, bites that tear as they penetrate.
Combine this with the jaw and cervical musculature denser than those of Tylosaurus proriger.
The result is a bite that crushed the prey’s skull instead of just securing the grip, as described in the study.
For context, this places Tylosaurus rex in an ecological niche similar to that of the modern great white shark.
Perhaps even more violent, because the great white shark measures between five and six meters, less than half the length of Tylosaurus rex.
The predator likely hunted other smaller mosasaurs, plesiosaurs, large fish, and even prehistoric sharks.
Another giant in the wave of recent discoveries
The Tylosaurus rex joins a recent sequence of paleontological discoveries of giants from the Upper Cretaceous.
Researchers in Thailand identified in May the Nagatitan chaiyaphumensis, a long-necked dinosaur measuring 27 meters and 28 tons.
There are at least five new species of prehistoric reptiles named just this month.
It’s circumstantial evidence that the pace of describing new Mesozoic vertebrates is accelerating.
The Perot Museum in Dallas, where part of the Tylosaurus rex material is stored, organized an exhibition about the species.
The mounted skeleton is in a room dedicated to fossils from the Western Interior Seaway.
By the way, it’s possible that Brazilian collections hold misidentified fossils of similar prehistoric reptiles.
Brazil has occurrences of smaller mosasaurs in deposits in Pernambuco and Sergipe.
Generally, poorly preserved fossils, but with real potential for future technical review.
I confess that this part fascinates me the most: paleontological discovery doesn’t just depend on digging new ground, but on looking again at what’s already in the museum drawer.
And you, which recent scientific discovery scared you the most because of the size of the creature? Tell us.
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