2023-12-13 15:33:29
The remains of a ‘mythological’ animal were hidden among the stones and sand of a large river in Japan. After more than 15 years of examination, some fossils found in 2006 in Japan have made it possible to describe a mosasaur similar to a great white sharkwhich terrorized the Pacific seas 72 million years ago.
The peculiarity of this monster is found in its rear fins extra long, which could have helped with propulsion along with its long tail. And unlike other mosasaurs, or large extinct marine reptiles, it had a shark-like dorsal fin that would have helped it turn quickly and precisely in the water.
The discovery, discovered by Associate Professor Takuya Konishi of the University of Cincinnati and his international co-authors, has been published in the Journal of Systematic Paleontology. This monosaurus was named after the place where it was found, Wakayama Prefecture. The researchers called it ‘Wakayama Soryu’which in Japanese translates to blue Dragon. “In China, dragons cause thunder and live in the sky, but in Japanese folklore they are aquatic creatures,” Konishi explained in a statement to justify his mythological nickname.
This particular specimen was discovered along the Aridagawa River in Wakayama by co-author Akihiro Misaki in 2006. The researcher was searching for invertebrate fossils when he found a dark fragment between the stone and the sand. At first he hesitated to examine it, not knowing if it was a fossil or a stone, but curiosity got the better of him. Closer examination revealed that it was a vertebra, part of a nearly complete mosasaur captured in the hard sandstone.
In fact, it is the most complete skeleton of a mosasaur ever found in Japan or the Pacific Northwest, according to researchers. “In this case, it was almost the entire specimen, which was amazing,” Konishi added.
Mosasaur discovered in Japan was the most complete skeleton ever found in Japan or the Pacific Northwest TAKUYA KONISHI
Superpredator contemporary to the T-Rex
Mosasaurs were apex predators in prehistoric oceans from about 100 million years ago to 66 million years ago, contemporaries of the T-Rex and other late Cretaceous dinosaurs that ruled the Earth. They survived any predator, but they were victims of the same mass extinction that wiped out almost all the dinosaurs when an asteroid crashed into what is now the Gulf of Mexico.
The Wakayama Soryu was about the size of a great white shark and lived more than 72 million years ago, during the era of Tyrannosaurus rex and other late Cretaceous Takumi dinosaurs.
The researchers placed the specimen in the subfamily Mosasaurinae and named it Megapterygius wakayamaensis to recognize where it was found. Megapterygius means “large winged”, in line with the enormous fins of the mosasaur that it could use to move with great speed.
Another prehistoric marine reptile, the plesiosaurio, used its fins for propulsion, but “did not have a long rudder-like tail,” the researcher said. “We lack any modern analogue that has this type of body morphology, from fish to penguins to sea turtles,” he said. “None have four large fins that they use along with a tail fin.”
The researchers speculated that the large front fins could have helped it with quick maneuvers, while its large rear fins could have provided the tilt needed to submerge or surface. And presumably, like other mosasaurs, its tail would have generated powerful and rapid acceleration while hunting fish.
“It’s a question of how these five hydrodynamic surfaces were used. What were they for the direction? Which ones for propulsion? he said. «This opens a whole can of worms that challenges our understanding of how mosasaurs swim».
The blue dragon had a dorsal fin similar to that of a great white shark that allowed it to maneuver precisely in the water
The possible ancestor of dolphins and porpoises
Wakayama Soryu apparently had a dorsal fin, based on the orientation of neural spines along its vertebrae. The study found that the orientation of these spines is remarkably similar to that of a harbor porpoise, which also has a prominent dorsal fin.
“It’s still hypothetical and speculative to some extent, but that distinctive change in neural column orientation behind a presumed center of gravity is consistent with today’s toothed whales that have dorsal fins, such as dolphins and porpoises,” they said. in the study.
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