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(STARKVILLE, MS) — Geologists working in Mississippi recently stumbled upon an incredible find: the fossil of an ancient marine apex predator.
They uncovered a piece of vertebra they said likely belonged to a mosasaur, a lizard ancestor that lived in the Late Cretaceous period, according to James Starnes, research director for the surface geology and surface mapping divisions for the Mississippi Department of Environmental Quality.
On April 15, researchers were collecting rock, sediment and fossil samples just south of Starkville, Mississippi, Starnes said. Poking out from the sediment of a creek bed was the end an “unusually large” lumbar vertebra.
After Starnes pointed it out, Jonathan Leard, the lead author of the MDEQ’s geological map, pulled the vertebra out of the clay.
“Both of us are standing there looking at each other with our jaws wide open because of the size,” Starnes said.
Starnes “immediately” knew they had found a mosasaur based on the shape of the vertebra, he said. The researchers estimated the specimen, determined to be Mosasaurus hoffmannii, was between 30 and 40 feet long when it died, but mosasaurs typically grew to be about 50 feet and weighed 20,000 pounds.
“These animals, like other lizards, are indeterminate,” Starnes said. “That means they just keep growing, with age, until they die.”
Due to its geological formations, the Mississippi region is known for its fossils, but this was especially rare, Starnes said.
Shell fossils are common, as are much younger Ice Age fossils from land animals, such as mastodons and sloths. But mosasaurs have a “very different” vertebra shape than other animals.
“This was distinctly not a mammal,” Starnes said. “This was definitely a sea lizard.”
Mosasaurs, a diverse group of marine lizards, conquered the seas in the Late Cretaceous period, a time when dinosaurs inhabited various ocean environments.
The Mississippi River occupies an ancient geologic structure called the Mississippi Embayment, which was inundated by the Western Interior Sea Way during the Cretaceous period.
Mosasaur fossils have been found in the area before, but only in much smaller fragments, Starnes noted. This was the largest mosasaur fossil the researchers had ever encountered.
Mosasaurs were fast and agile swimmers with jaws that contained 60 dagger-like teeth that helped them capture large prey, researchers said.
Scientists believe mosasaurs became extinct at the end of the Cretaceous period, according to Mississippi Department of Environmental Quality researchers.
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