Dino card No. 1158 of 2,027

Megapterygius

Say it: MEG-ap-ter-IJ-ee-us

Name means: “large wing”1

Ate: MeatMosasaursLate CretaceousNot technically a dinosaur

Megapterygius was a huge marine lizard that swam in the seas around Japan 72 million years ago. It had enormous flippers that were longer than its head, and scientists think it even had a dorsal fin like a shark!1 2

Fun fact: this sea reptile swam while dinosaurs walked on land. Everyone calls them dinos, but they were a different branch of reptiles.

Lived

84 to 66 million years ago4

Late Cretaceous

Fossils found in

Wakayama Prefecture, Japan1

Food

Meat1 2

Length

6 m1

estimated

Weight

150 kg to 450 kg3

estimate

When did it live?

Triassic

Jurassic

Cretaceous

252 million years ago20114566, the asteroid

How big was it?

How long was it?

How heavy was it?

as heavy as 15 big dogs

as long as 6 dogs nose to tailas long as 33 bananas end to endas heavy as 90 watermelons

How big was Megapterygius compared to YOU?

Just maths in your browser. Nothing is saved or sent anywhere.

cool stuff

Fun facts

Megapterygius had rear flippers that were even longer than its front flippers, a feature only seen in one other mosasaur, Tylosaurus.1

Its flippers were longer than its skull, which is unique among mosasaurs with paddle-like limbs.1

The shape of its backbone suggests it had a dorsal fin, like a dolphin or shark, which would have helped it turn quickly in the water.1 2

Its skull was slightly wide around the eye sockets, giving it binocular vision that helped it hunt prey. This is only the second mosasaur known to have this ability.1

The fossil was found in 2006 by Akihiro Misaki, who was actually looking for ammonite fossils when he spotted a vertebra.1 2

More than 100 shark teeth were found around the Megapterygius skeleton, suggesting that sharks scavenged its body after it died.1

Megapterygius is the most complete mosasaur skeleton ever found in Japan or the northwestern Pacific.2

AI-made picture of Megapterygius — An AI-made picture of how Megapterygius might have looked, made by a computer from what scientists know. It is a guess: the real animal may have looked different, and nobody knows its true colours.

you asked

Most asked questions about Megapterygius

?How big was Megapterygius?

Megapterygius was about 6 metres long, with a skull about 0.8 metres long. That is roughly the size of a large great white shark.1 2

?Did Megapterygius have a dorsal fin?

Scientists think it did. The shape of its backbone is like that of dolphins and porpoises, which have dorsal fins, and this would have helped it turn quickly in the water. It's the first mosasaur with evidence of a dorsal fin.1 2

?What did Megapterygius eat?

Scientists think it hunted large groups of small prey, like schools of fish. Its binocular vision and big flippers would have helped it catch them.1

?When did Megapterygius live?

Megapterygius lived about 72 million years ago, during the Late Cretaceous period, in the seas around Japan.1 2

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For dino experts

Scientific name: Megapterygius
Named by: Konishi et al. 20234
Group: Mosasaurs
Family / clade: Mosasauridae4
Classification: Mosasauroidea4
Age of the rocks: 84 to 66 million years (Campanian / Maastrichtian)4
Rock formations: Toyajo4
Countries: Japan4
Fossil records: 1 in the Paleobiology Database4
Discovery: The fossil was discovered in 2006 by Akihiro Misaki in Wakayama Prefecture, Japan. It was named Megapterygius wakayamaensis by Takuya Konishi and colleagues in 2023.1 2
Still debated: Scientists are still debating how Megapterygius used its four large flippers and tail fin together for swimming, since no modern animal has a similar body shape.2

Where the facts come from

Megapterygius (en.wikipedia.org)
UC paleontologist describes Wakayama 'blue dragon' that ruled prehistoric waters off Japan - University of Cincinnati: Founder of Co-op, Leader in Co-op | University of Cincinnati (uc.edu)
Megapterygius | Dino Encyclopedia (dinosaurmuseum.jp)
Megapterygius in The Paleobiology Database (CC BY 4.0): age, places, rock formations, classification.

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