Newly identified species could shed light on evolution of prehistoric ‘sea monsters’

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An infinite sea snake from Norse legend that was fathered by the trickster god Loki and grew large enough to circle the globe is now the namesake for a unique sort of “monster” — a newly found species of an enormous, meat-eating marine reptile often called a mosasaur, which lived about 80 million years in the past.

Paleontologists just lately described the beforehand unknown mosasaur from fossils discovered close to the North Dakota city of Walhalla. The city’s identify comes from Valhalla, the feasting corridor of Norse mythology the place lifeless heroes collect, so the scientists dubbed the mosasaur Jormungandr walhallaensis. Its identify references Norse myths of Jǫrmungandr, the Midgard Serpent, in addition to the location of the fossil’s discovery, the researchers reported Monday within the journal Bulletin of the American Museum of Natural History.

The fossil itself has a considerably much less poetic identify: NDGS 10838. It features a near-complete cranium with a bony ridge over the eyes in addition to jaws and a few skeletal elements, together with 11 ribs and 12 vertebrae. In life, the animal would have measured about 24 toes (7.3 meters) lengthy and had an extended face slimmer than these of its mosasaur cousins, stated lead examine writer Amelia Zietlow, a paleontologist and doctoral candidate on the American Museum of Pure Historical past’s Richard Gilder Graduate Faculty in New York Metropolis.

Typically, Jormungandr walhallaensis resembled most mosasaurs — “sort of like when you took a Komodo dragon, made it 30 toes lengthy and gave it flippers and a shark tail,” Zietlow instructed CNN.

But in different methods, the animal was considered one of a form. A mixture of options within the bones of its cranium made it unexpectedly difficult for the scientists to categorise the newcomer and hinted that the mosasaur group contains extra various types than anticipated, the examine authors reported.

The fossil was collected in 2015 by the North Dakota Geological Survey, a state company devoted to geology and public training about minerals and fossils. In reality, Zietlow stated, NDGS 10838 was found in a hillside by somebody who had participated in one of many company’s packages, and who was due to this fact capable of acknowledge the thing as a fossil and knew to alert company officers.

When the scientists examined the cranium, they shortly realized that they had one thing uncommon on their fingers. Its ear bones, which had been considerably rectangular, resembled these of Mosasaurus, the genus of mosasaur giants. However the form and excessive variety of its enamel had been a more in-depth match to a genus of smaller mosasaurs: Clidastes. In the meantime, the angle and variety of enamel on a bony palate on the roof of its mouth had been in contrast to something seen in both of these two mosasaur teams.

“He’s bought options that look in some methods like Mosasaurus, in some methods like Clidastes. After which in different methods, they’re fully distinctive to this particular person,” Zietlow stated. This mix of traits satisfied the researchers that what they had been taking a look at was a brand new genus and species.

Here is a line drawing of the skull of the Jormungandr walhallaensis. A mix of features in the bones of its skull made it challenging for scientists to classify it.

Nonetheless, fossilization usually distorts bone, and it’s potential that oddities within the fossil had been formed by pure processes after the animal’s dying, stated paleontologist Takuya Konishi, an affiliate professor within the division of organic sciences on the College of Cincinnati. (The authors acknowledged this risk; their examine contains idealized illustrations of the intact cranium exhibiting what it might have seemed like earlier than it fossilized.)

When the researchers analyzed the info, their evolutionary tree confirmed an consequence known as a polytomy — “when a bunch of various species sort of blur collectively right into a single spot” — with Jormungandr walhallaensis and Clidastes, Zietlow stated. “They’re nearer to one another than they’re to the rest. However inside that group of issues, it’s not fairly positive how they’re associated.”

Further fossils of the newfound species may assist fine-tune Jormungandr walhallaensis’ place on the mosasaur household tree, stated Konishi, who research mosasaur evolution and was not concerned within the examine.

“Simply how distinct J. walhallaensis is from Clidastes has but to be investigated additional,” Konishi instructed CNN in an e mail. “Future discoveries could favor another speculation that it’s a new species of Clidastes.”

Different uncommon particulars within the fossil are punctures and scratches scarring the vertebrae; the researchers recognized these as chunk marks. The marks don’t seem to have healed, suggesting that they occurred towards the top of the animal’s life or had been the work of a scavenger that ripped the mosasaur aside after it was lifeless.

“This is likely to be why we don’t have the remainder of the skeleton,” Zietlow stated.

Additional questions on what made the marks — and whether or not it was an assault that Jormungandr walhallaensis survived — will likely be addressed in future analysis by examine coauthor Clint Boyd, a senior paleontologist with the North Dakota Geological Survey and a curator of the North Dakota State Fossil Assortment, Zietlow stated.

Mosasaurs and evolutionary enigmas

Mosasaurs had been a various group of apex predators that swam the world’s oceans through the latter a part of the Cretaceous Interval, about 98 million to 66 million years in the past. They lived alongside dinosaurs however are extra intently associated to fashionable lizards and snakes.

Some mosasaurs measured just some toes lengthy, whereas the biggest — within the genus Mosasaurus — was practically 60 toes (18.2 meters) lengthy, and whereas mosasaur fossils are comparatively plentiful, scientists “have simply solely scratched the floor of the ‘true’ mosasaur range,” Konishi stated. New mosasaur specimens, similar to NDGS 10838, assist consultants to unravel “the wealthy evolutionary historical past of those somewhat charismatic apex predators of the Cretaceous seas,” he stated.

To that finish, the brand new examine makes a major contribution by supplying “wealthy anatomical element documented by a really ready mosasaur employee, Ms. Zietlow,” he added.

“The authors clearly supplied a really thorough and cautious osteological description of the brand new specimen,” making a treasure trove of outstanding information, Konishi stated.

Although mosasaurs had been aquatic, their ancestors lived on land after which advanced to return to the ocean. They weren’t the one animal group to take action; many varieties of reptiles and mammals — together with plesiosaurs, whales, sea turtles and seals — tailored to ocean life from terrestrial ancestors, lengthy after their much more distant tetrapod ancestors left the seas for land. And mosasaurs are an essential animal group for finding out this transition as a result of their fossils are so plentiful, Zietlow stated.

“There are quite a lot of them, actually hundreds of specimens in the USA alone,” she stated. “That makes them good for finding out large image, statistical-type evolutionary questions.”

Regardless of the plentiful pool of specimens, many mosasaur fossils weren’t documented as exhaustively as Jormungandr walhallaensis was (and in some circumstances, had been barely illustrated in any respect once they had been first described, Zietlow stated).

Addressing this discrepancy in newfound fossils — and revisiting recognized specimens — will play an enormous half in serving to scientists remedy these evolutionary riddles.

“I spent quite a lot of time placing collectively these figures, exhibiting the bones in each view and exhibiting the entire little lumps and bumps and issues, in order that future folks can take a look at these figures and acknowledge the anatomy after which apply that to creating new characters and recognizing new variations between this animal and different animals,” Zietlow stated. “That simply helps everybody general to grasp the anatomy of these items a little bit bit higher.”

Mindy Weisberger is a science author and media producer whose work has appeared in Dwell Science, Scientific American and How It Works journal.

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