Dino card No. 1137 of 2,027

Marambionectes

Say it: mah-RAM-bee-oh-NEK-teez

Name means: “Marambio Island swimmer”1

Ate: MeatPlesiosaursLate CretaceousNot technically a dinosaur

Marambionectes was a long-necked marine reptile that swam in the seas near Antarctica about 70 million years ago. It was not a dinosaur, but a fierce hunter that used its flippers to glide through the water.1 3

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

Lived

72 to 66 million years ago3

Late Cretaceous

Fossils found in

Antarctica, on Marambio (Seymour) Island in the López de Bertodano Formation1 3

Food

Meat3

When did it live?

Triassic

Jurassic

Cretaceous

252 million years ago20114566, the asteroid

cool stuff

Fun facts

Marambionectes had 48 neck vertebrae, and the 5th to 29th of these had special side keels, a feature not seen in other elasmosaurids.2

Its lower jaw had three tooth sockets at the front and a wide groove, which helped scientists link it to a group called aristonectines.2

The fossil skeleton was found in 2018 and includes parts of the skull, many vertebrae, ribs, and limb bones, all from an adult animal.1

Scientists think Marambionectes was closely related to the aristonectines, a group of elasmosaurids with short necks and big heads.1 2

The name honors Omar J. Molina, an Argentinian fossil preparator who worked in Antarctica.1

AI-made picture of Marambionectes — An AI-made picture of how Marambionectes 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.

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Myth buster

Myth: Some people think all plesiosaurs were dinosaurs.

Truth: Plesiosaurs like Marambionectes were marine reptiles, not dinosaurs. Dinosaurs lived on land and had different body features.1

For dino experts

Scientific name: Marambionectes
Named by: O’Gorman et al. 20243
Group: Plesiosaurs
Family / clade: Elasmosauridae3
Classification: Plesiosauria > Elasmosauridae > Sauropterygia3
Age of the rocks: 72 to 66 million years (Maastrichtian)3
Rock formations: López de Bertodano3
Countries: Antarctica3
Fossil records: 1 in the Paleobiology Database3
Discovery: The fossil was found in 2018 on Marambio Island, Antarctica, and was named by O'Gorman and colleagues in 2024.1 3
Still debated: Scientists are still debating exactly how Marambionectes is related to other elasmosaurids, especially whether it belongs inside or just outside the aristonectine group.1 2

Where the facts come from

Marambionectes (en.wikipedia.org)
Description: A new elasmosaurid (Plesiosauria :: NVK CVTI SR (ersearch2.cvtisr.sk)
Marambionectes in The Paleobiology Database (CC BY 4.0): age, places, rock formations, classification.

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