Dino card No. 0670 of 2,027

Fresnosaurus

Say it: FRES-noh-SORE-us

Name means: “Fresno lizard, named after Fresno County in California”1

Ate: MeatPlesiosaursLate CretaceousNot technically a dinosaur

Fresnosaurus was a huge swimming reptile with a very long neck and flippers instead of legs. It lived in the sea near California during the time of the dinosaurs, but it was not a dinosaur. It probably used its long neck to sneak up on fish and other small sea creatures.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

Fresno County, California, USA, in the Moreno Formation1 2

Food

Meat1 3

Length

up to 9 m1

at least 9 meters, based on estimates

When did it live?

Triassic

Jurassic

Cretaceous

252 million years ago20114566, the asteroid

How big was it?

as long as 2 cars parked in a rowas long as 50 bananas end to end

How big was Fresnosaurus compared to YOU?

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

cool stuff

Fun facts

Fresnosaurus lived about 70 to 66 million years ago, right at the end of the Age of Dinosaurs.1

The only known fossil is from a young animal, so scientists think adults might have been even bigger than 9 meters (30 feet).2

Its name honors Fresno County, and the species name 'drescheri' honors Arthur Drescher, who likely helped find the fossil.1

Fresnosaurus belonged to a group called elasmosaurids, famous for their extremely long necks and paddle-like flippers.1 3

The fossil includes bones like the coracoids (shoulder bones), humerus (upper arm bone), pelvic girdle, and femora (thigh bones), but no skull has been found.2

Scientists recently found that some extra bones labeled as Fresnosaurus might actually belong to a different, related plesiosaur called an aristonectine.2

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

Ask Rex about Fresnosaurus

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Myth buster

Myth: Some people think Fresnosaurus was a dinosaur because it lived with dinosaurs and is often shown in dinosaur books.

Truth: Fresnosaurus was a plesiosaur, a marine reptile, not a dinosaur. Dinosaurs lived on land and had different body shapes.1 3

For dino experts

Scientific name: Fresnosaurus
Named by: Welles 19433
Group: Plesiosaurs
Family / clade: Elasmosauridae3
Classification: Plesiosauria > Elasmosauridae > Sauropterygia3
Age of the rocks: 72 to 66 million years (Maastrichtian)3
Rock formations: Moreno3
Countries: USA3
Fossil records: 1 in the Paleobiology Database3
Discovery: Fresnosaurus was first described by Samuel Paul Welles in 1943, based on a fossil found in the Moreno Formation of California. The fossil was originally stored at the California Institute of Technology and is now at the Natural History Museum of Los Angeles County.1 2
Still debated: Scientists are still debating whether Fresnosaurus is a valid, separate genus or if it might be the same as another elasmosaurid, because the only fossil is incomplete and from a juvenile.2

Where the facts come from

Fresnosaurus (en.wikipedia.org)
Reappraisal of Fresnosaurus drescheri (Plesiosauria; Elasmosauridae) from the Maastrichtian Moreno Formation, California, USA - ScienceDirect (sciencedirect.com)
Fresnosaurus 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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