This Japanese 'dragon' terrorized ancient seas

Researchers have described a Japanese mosasaur the size of a great white shark that terrorized Pacific seas 72 million years ago.

Extra-long rear flippers might have aided propulsion in concert with its long finned tail.

And unlike other mosasaurs, or large extinct marine reptiles, it had a dorsal fin like a shark's that would have helped it turn quickly and with precision in the water.

University of Cincinnati Associate Professor Takuya Konishi and his international co-authors described the mosasaur and placed it in a taxonomic context in the Journal of Systematic Palaeontology.

The mosasaur was named for the place where it was found, Wakayama Prefecture.

Researchers call it the Wakayama Soryu, which means blue dragon.

Dragons are creatures of legend in Japanese folklore, Konishi said.

"In China, dragons make thunder and live in the sky. They became aquatic in Japanese mythology," he said.

The specimen was discovered along the Aridagawa River in Wakayama by co-author Akihiro Misaki in 2006.

The specimen is the most complete skeleton of a mosasaur ever found in Japan or the northwestern Pacific, Konishi said.

"In this case, it was nearly the entire specimen, which was astounding," Konishi said.

He has dedicated his career to studying these ancient marine reptiles.

But the Japanese specimen has unique features that defies simple classification, he said.

Its rear flippers are longer than its front ones. These enormous flippers are even longer than its crocodile-like head, which is unique among mosasaurs.

"I thought I knew them quite well by now," Konishi said. "Immediately it was something I had never seen before."

Mosasaurs were apex predators in prehistoric oceans from about 100 million years ago to 66 million years ago.

They were contemporaries of Tyrannosaurus rex and other late Cretaceous dinosaurs that ruled the Earth.

Mosasaurs were victims of the same mass extinction that killed off nearly all dinosaurs when an asteroid struck what is now the Gulf of Mexico.

Researchers placed the specimen in the subfamily Mosasaurinae and named it Megapterygius wakayamaensis to recognize where it was found.

Megapterygius means "large winged" in keeping with the mosasaur's enormous flippers.

Konishi said those big paddle-shaped flippers might have been used for locomotion.

But that type of swimming would be extraordinary not only among mosasaurs but among virtually all other animals.

"We lack any modern analog that has this kind of body morphology -- from fish to penguins to sea turtles," he said.

"None has four large flippers they use in conjunction with a tail fin."

Researchers speculated that the large front fins might have helped with rapid maneuvering while its large rear fins might have provided pitch to dive or surface.

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New species of mosasaur named for Norse sea serpent

Scientists have discovered a new species of mosasaur, large, carnivorous aquatic lizards that lived during the late Cretaceous. With "transitional" traits that place it between two well-known mosasaurs, the new species is named after a sea serpent in Norse mythology, Jormungandr, and the small North Dakota city Walhalla near to where the fossil was found. Details describing Jormungandr walhallaensis are published today in the Bulletin of the American Museum of Natural History.

"If you put flippers on a Komodo dragon and made it really big, that's basically what it would have looked like," said the study's lead author Amelia Zietlow, a Ph.D. student in comparative biology at the American Museum of Natural History's Richard Gilder Graduate School.

The first mosasaur was discovered more than 200 years ago, and the word "mosasaur" predates the word "dinosaur." But many questions about these animals remain, including how many times they evolved flippers and became fully aquatic -- researchers think it was at least three times, and maybe four or more -- and whether they are more closely related to monitor lizards or snakes. Researchers are still trying to determine how the different groups of mosasaurs are related to each other, and the new study adds a new piece to that puzzle.

The fossil on which the study is based was discovered in 2015, when researchers excavating in the northeastern part of North Dakota found an impressive specimen: a nearly complete skull, jaws, and cervical spine, as well as a number of vertebrae.

After extensive analysis and surface scanning of the fossil material, Zietlow and her collaborators found that this animal is a new species with a mosaic of features seen in two iconic mosasaurs: Clidastes, a smaller and more primitive form of mosasaur; and Mosasaurus, a larger form that grew to be nearly 50 feet long and lived alongside Tyrannosaurus rex. The specimen is estimated to be about 24 feet long, and in addition to flippers and a shark-like tail, it would have had "angry eyebrows" caused by a bony ridge on the skull, and a slightly stumpy tail that would have been shorter than its body.

"As these animals evolved into these giant sea monsters, they were constantly making changes," Zietlow said. "This work gets us one step closer to understanding how all these different forms are related to one another."

The work suggests that Jormungandr was a precursor to Mosasaurus and that it would have lived about 80 million years ago.

"This fossil is coming from a geologic time in the United States that we don't really understand," said co-author Clint Boyd, from the North Dakota Geological Survey. "The more we can fill in the geographic and temporal timeline, the better we can understand these creatures."

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