Researchers have made an incredible discovery: a Japanese mosasaur the size of a great white shark that terrorized Pacific seas 72 million years ago.
What makes this mosasaur so unique is its extra-long rear flippers that might have aided propulsion along with its long finned tail. Unlike other mosasaurs, it had a dorsal fin like a shark’s, allowing for quick and precise movements 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.
Named after the place where it was found, this mosasaur was called the Wakayama Soryu, which means blue dragon, fitting for a creature of legend in Japanese folklore. In Japan, dragons are aquatic creatures that live in the sea, unlike Chinese dragons that live in the sky and make thunder, Konishi explained.
What makes this discovery even more special is that it is the most complete skeleton of a mosasaur ever found in Japan or the northwestern Pacific, discovered along the Aridagawa River in Wakayama. Co-author Akihiro Misaki found the specimen in 2006, calling it “astounding.”
The Japanese mosasaur has unique features that have puzzled researchers. Its rear flippers are longer than its front ones, which is unlike any other mosasaur discovered before.
Mosasaurs were apex predators in prehistoric oceans and were contemporaries of Tyrannosaurus rex and other late Cretaceous dinosaurs. They were victims of the mass extinction event caused by an asteroid strike, which led to the demise of nearly all dinosaurs.
Named Megapterygius wakayamaensis to recognize the location of its discovery, the Japanese mosasaur challenges our understanding of how these ancient creatures swam with its extraordinary body morphology and large flippers.
Researchers speculated the large front fins might have helped with rapid maneuvering while its large rear fins might have provided pitch to dive or surface. And presumably, like other mosasaurs, its tail would have generated powerful and fast acceleration as it hunted fish.
This groundbreaking discovery opens a new chapter in our understanding of the prehistoric world and how ancient marine reptiles lived and moved.