Dino card No. 0168 of 2,027

Aristonectes

Say it: AIR-iss-TON-ek-teez

Name means: “best swimmer”1

Ate: MeatPlesiosaursLate CretaceousNot technically a dinosaur

Aristonectes was a huge marine reptile that swam in the seas near Antarctica and South America at the end of the Age of Dinosaurs. It had a big head, a short neck, and a body shaped a bit like a whale. It used its wide mouth to suck up food from the seafloor, just like a gray whale does today.1

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

Argentina, Chile, and Antarctica4 1

Food

Meat1

Length

10 to 11.9 m1

estimates for different specimens

Weight

4.2 tonnes to 13.5 tonnes1

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 2 elephants

as long as 2.5 cars parked in a rowas long as 66 bananas end to endas heavy as 9 carsas heavy as 2700 watermelons

How big was Aristonectes compared to YOU?

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cool stuff

Fun facts

Aristonectes is one of the biggest and heaviest plesiosaurs ever found. One Antarctic specimen may have weighed as much as 13.5 metric tons (about 15 tons), as heavy as a large school bus.1

Unlike most plesiosaurs, which had very long necks, Aristonectes had a short neck and a big, bulky skull. Scientists put it in a special group called Aristonectinae because of this.1

Aristonectes probably migrated between Patagonia and Antarctica, just like many whales do today. Its fossils are found in both places.1

The first fossils of Aristonectes were discovered in Argentina in 1941, but scientists had a hard time studying them because the bones were not well prepared. It took decades to figure out what kind of plesiosaur it was.1

Aristonectes had a mouth that could open very wide, letting it gulp a huge amount of water and food at once. It fed by mixing prey with sediment from the seafloor, a method called benthic suction feeding.1

Like other plesiosaurs, Aristonectes probably swallowed stones called gastroliths. These may have helped grind up food in its stomach or helped control its buoyancy in the water.1

AI-made picture of Aristonectes — An AI-made picture of how Aristonectes 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 Aristonectes

?How big was Aristonectes?

Aristonectes was huge, measuring more than 10 metres (33 feet) long. One Antarctic specimen may have reached 11 to 11.9 metres (36 to 39 feet) and weighed 10.7 to 13.5 metric tons (11.8 to 14.9 short tons).1 2

?What did Aristonectes eat?

Aristonectes likely ate crustaceans and small fish, based on its small teeth. It fed by sucking up prey and sediment from the seafloor, like a gray whale.1 3

?Was Aristonectes a dinosaur?

No, Aristonectes was a plesiosaur, a marine reptile that lived alongside the dinosaurs. It was not a dinosaur.1

?Where did Aristonectes live?

Aristonectes lived in the seas near Patagonia and Antarctica during the Late Cretaceous. Its fossils have been found in Chile, Argentina, and Antarctica.1

?Could Aristonectes swim?

Yes, Aristonectes was a strong swimmer, using its large paddle-like limbs to move through the water. Its name means 'best swimmer'.1

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For dino experts

Scientific name: Aristonectes
Named by: Cabrera 19414
Group: Plesiosaurs
Family / clade: Elasmosauridae4
Classification: Plesiosauria > Elasmosauridae > Sauropterygia4
Age of the rocks: 84 to 66 million years (Campanian / Maastrichtian)4
Rock formations: Quiriquina, López de Bertodano, Lopez de Bertodano4
Countries: Chile, Antarctica, Argentina4
Fossil records: 12 in the Paleobiology Database4
Also known as: Turneria (older names now counted as the same animal)4
Discovery: Aristonectes was named by Argentine paleontologist Ángel Cabrera in 1941, based on fossils found in Chubut, Argentina. The first species named was Aristonectes parvidens.1 4
Still debated: Scientists are still debating exactly how Aristonectes is related to other plesiosaurs. For a long time it was thought to be a cryptoclidid, but now most agree it is an elasmosaurid.1

Where the facts come from

Aristonectes (en.wikipedia.org)
A giant elasmosaurid (Sauropterygia; Plesiosauria) from Antarctica: New information on elasmosaurid body size diversity and aristonectine evolutionary scenarios (sciencedirect.com)
Fossil 'sea monster' found in Antarctica was the heaviest of its kind | National Geographic (nationalgeographic.com)
Aristonectes in The Paleobiology Database (CC BY 4.0): age, places, rock formations, classification.

Every fact on this page has a number that points to its source. If we got something wrong, sorry, we are dino fans, not a science journal. Tell us at [email protected] and we will fix it.

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