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About 80 million years ago, when dinosaurs walked on Earth, an 18 foot long (5 meter) sea monster called a mosasaur sailed the ancient ocean that once covered western Kansas, grabbing prey with its slender, tooth-rimmed snout.
Paleontologists discovered the fossil of this beast in the 1970s, but struggled to classify it, so it ended up being stored with other mosasaur specimens in the Platecarpus kind, at the Sternberg Museum of Natural History (FHSM) at Fort Hays State University in Kansas.
Recently, researchers revisited the enigmatic fossil – pieces of skull, jawbone, and a few bones from behind the head – and found that the reptile did not belong to the Platecarpus kind. Rather, it was a close relative of a rare species of mosasaur known from a single specimen, scientists have reported in a new study.
Related: Image gallery: Ancient sea monsters
The newly described species, formerly known as the FHSM VP-5515 specimen and now named Ectenosaurus everhartorum, is the second known species in the Ectenosaurus kind. The only other species is Ectenosaurus clidastoides, which was first described in 1967, according to the study.
E. everhartorumthe head was about 2 feet (0.6 m) long, and like E. clidastoids, E. everhartorum had a narrow and elongated muzzle compared to that of other mosasaurs, said study co-author Takuya Konishi, a vertebrate paleontologist and assistant professor at the University of Cincinnati.
“It’s kind of a lean snout for snapping nimble, fast fish, rather than biting into something hard like turtle shells,” Konishi told Live Science. The narrowness of the jaw and a bone at the top of the head suggested that VP-5515 belonged to the Ectenosaurus genus, although the fossil was about 500,000 to 1 million years younger than the E. clidastoids specimen, says Konishi.
But in some ways the skull was not Ectenosaurus-like at all. For example, he was missing a bone lump at the end of his muzzle. The muzzle of the VP-5515 was also shorter than that of the E. clidastoids, according to the study.
“We knew it was a new species, but we didn’t know if it was a Ectenosaurus or not, ”Konishi said. “To answer this riddle, we were finally able to find another feature where the jaw joint was, at the back of the lower jaw. There, the researchers detected a small notch that did not appear. in all mosasaur species – except one.
“This little depression turned out to be a newly discovered consistent feature for the genre. Ectenosaurus“Konishi said.” You have this Ectenosaurus united by the small notch at the end of the lower jaw, but then it is systematically different at the level of the species from the generic type, that is to say from the first species assigned to the genus.
A lingering question about Ectenosaurus This is why this genus is so poorly represented among mosasaur fossils from western Kansas. To date, paleontologists have discovered more than 1,800 mosasaur specimens at the site of the ancient Inland Sea. But for now, the whole Ectenosaurus The genus is only represented by two fossils, one for each species.
“It’s very strange,” Konishi told Live Science. “Why is it so rare for a mosasaur, where you have hundreds of Platecarpus from the same locality? Does that mean they lived near the shore, or did they live further south or further north? We just don’t know. “
The results were published on August 26 in the Canadian Journal of Earth Sciences.
Originally posted on Live Science.
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