In 2006, Akihiro Misaki, a paleontologist with the Kitakyushu Museum of Natural History and Human History, made a remarkable discovery near the Aridagawa River in Wakayama, Japan.
He unearthed a nearly intact skeleton of a prehistoric marine dinosaur, a find that took half a decade to excavate completely and revolutionized knowledge of ancient marine life.
Uncovered from the depths of history, the Megapterygius wakayamaensis, a six-meter- (20-foot-) long mosasaur as long as a minibus, lived over 72 million years ago. The formal description of this air-breathing marine lizard species posed a new puzzle for paleontologists.
Takuya Konishi, a paleontologist from the University of Cincinnati, explained the challenges in understanding the creature's locomotion and hunting strategies.
"We lack any modern analog that has this kind of body morphology – from fish to penguins to sea turtles. None has four large flippers they use in conjunction with a tail fin," Konishi told a news source.
Wakayama 'blue dragon' - Megapterygius wakayamaensis
© Photo : Takuya Konishi
Despite being warm-blooded, Megapterygius was neither a mammal nor a crocodilian — although its head resembled a crocodile's. Its most striking features included dual eyesight, massive paddle-shaped limbs, a robust tail, and potentially a dorsal fin. This combination of attributes was so unique that scientists in Japan named it the Wakayama 'blue dragon,' a mythical creature from Japanese folklore.
Mosasaurs were the apex predators of the oceans for about 20 million years. They were formidable creatures, stretching up to 17 meters (55.8 ft), with powerful jaws and sharp teeth capable of preying on a wide range of marine life — including their own kind.
The Wakayama blue dragon is notable for its extended rear flippers and spine resembling a dolphin, indicating unique adaptations like a dorsal fin and a distinct swimming method. Unlike other mosasaurs, it likely used its front fins for maneuvering and back fins for diving or surfacing, similar to cetaceans like dolphins. This is distinct from plesiosaurs, which relied on their flippers for propulsion.
Konishi said the creature's swimming adaptations highlight the find's significance:
"It is a question of just how all five of these hydrodynamic surfaces were used. Which were for steering? Which is for propulsion? It opens a whole can of worms that challenge our understanding of how mosasaurs swim," the paleontologist said.
This discovery not only adds a new species to the paleontological record but also invites a re-evaluation of our knowledge about marine reptile locomotion and ecology during the age of the dinosaurs.