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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Tiniest ever ancient seawater pockets revealed

Trapped for millennia, the tiniest liquid remnants of an ancient inland sea have now been revealed. The surprising discovery of seawater sealed in what is now North America for 390 million years opens up a new avenue for understanding how oceans change and adapt with the changing climate. The method may also be useful in understanding how hydrogen can be safely stored underground and transported for use as a carbon-free fuel source.

"We discovered we can actually dig out information from these mineral features that could help inform geologic studies, such as the seawater chemistry from ancient times," said Sandra Taylor, first author of the study and a scientist at the Department of Energy's Pacific Northwest National Laboratory.

Taylor worked with PNNL colleagues Daniel Perea, John Cliff, and Libor Kovarik to perform the analyses in collaboration with geochemists Daniel Gregory of the University of Toronto and Timothy Lyons of the University of California, Riverside. The research team reported their discovery in the December 2022 issue of Earth and Planetary Science Letters.

Ancient seas; modern tools

Many types of minerals and gems contain small pockets of trapped liquid. Indeed, some gemstones are prized for their light-catching bubbles of liquid trapped within. What's different in this study is that scientists were able to reveal what was inside the tiniest water pockets, using advanced microscopy and chemical analyses.

The findings of the study confirmed that the water trapped inside the rock fit the chemistry profile of the ancient inland saltwater sea that once occupied upstate New York, where the rock originated. During the Middle Devonian period, this inland sea stretched from present day Michigan to Ontario, Canada. It harbored a coral reef to rival Australia's Great Barrier Reef. Sea scorpions the size of a pickup truck patrolled waters that harbored now-extinct creatures like trilobites, and the earliest examples of horseshoe crabs.

But eventually the climate changed, and along with that change, most of the creatures and the sea itself disappeared, leaving behind only fossil remains embedded in sediments that eventually became the pyrite rock sample used in the current experiment.

Clues to an ancient climate and to climate change

Scientists use rock samples as evidence to piece together how the climate has changed over the long span of geologic time.

"We use mineral deposits to estimate the temperature of the ancient oceans," said Gregory, a geologist at the University of Toronto, and one of the study leaders. But there are relatively few useful examples in the geological record.

"Salt deposits from trapped seawater [halite] are relatively rare in the rock record, so there are millions of years missing in the records and what we currently know is based on a few localities where there is halite found," Gregory said. By contrast, pyrite is found everywhere. "Sampling with this technique could open up millions of years of the geologic record and lead to new understanding of changing climate."

Seawater surprise

The research team was trying to understand another environmental issue -- toxic arsenic leaching from rock -- when they noticed the tiny defects. Scientists describe the appearance of these particular pyrite minerals as framboids -- derived from the French word for raspberry -- because they look like clusters of raspberry segments under the microscope.

"We looked at these samples through the electron microscope first, and we saw these kind of mini bubbles or mini features within the framboid and wondered what they were," Taylor said.

Using the precise and sensitive detection techniques of atom probe tomography and mass spectrometry -- which can detect minuscule amounts of elements or impurities in minerals -- the team worked out that the bubbles indeed contained water and their salt chemistry matched that of ancient seas.

From ancient sea to modern energy storage

These types of studies also have the potential to provide interesting insights into how to safely store hydrogen or other gases underground.

"Hydrogen is being explored as a low-carbon fuel source for various energy applications. This requires being able to safely retrieve and store large-amounts of hydrogen in underground geologic reservoirs. So it's important to understand how hydrogen interacts with rocks," said Taylor. "Atom probe tomography is one of the few techniques where you can not only measure atoms of hydrogen, but you can actually see where it goes in the mineral. This study suggests that tiny defects in minerals might be potential traps for hydrogen. So by using this technique we could figure out what's going on at the atomic level, which would then help in evaluating and optimizing strategies for hydrogen storage in the subsurface."

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