Dino card No. 0842 of 2,027

Hydrotherosaurus

Say it: hy-dro-THEER-oh-SORE-us

Name means: “fisherman lizard”1

Ate: MeatPlesiosaursLate CretaceousNot technically a dinosaur

Hydrotherosaurus was a long-necked marine reptile that swam in the seas near California about 70 million years ago. It used its tiny head and super long neck to sneak up on fish and snap them up.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

72 to 66 million years ago2

Late Cretaceous

Fossils found in

Panoche Hills, Fresno County, California, USA1 2

Food

Meat1 2

Length

7.8 to 8.8 m1

estimate

Weight

1.9 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 1.5 cars

as long as 9 dogs nose to tailas long as 49 bananas end to endas heavy as 63 big dogsas heavy as 380 watermelons

How big was Hydrotherosaurus compared to YOU?

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cool stuff

Fun facts

Hydrotherosaurus had one of the longest necks compared to its body of any elasmosaur, with 60 vertebrae in its neck.1

Its head was very small, only about 33 centimetres (13 inches) long.1

The first bones were found by Frank C. Paiva on his own property in California in 1937.1

A nearly complete skeleton was dug up and put on display at the Golden Gate International Exposition in San Francisco.1

It weighed about 1.9 metric tons (2.1 short tons), as heavy as a small car.1

Hydrotherosaurus lived in the Late Cretaceous period, between about 72 and 66 million years ago.1 2

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

?How big was Hydrotherosaurus?

Hydrotherosaurus was about 7.8 to 8.8 metres long and weighed around 1.9 metric tons.1

?What did Hydrotherosaurus eat?

It was an active, fish-eating animal, using its long neck and small head to snap up fish.1 2

?When did Hydrotherosaurus live?

It lived during the Late Cretaceous period, about 72 to 66 million years ago.1

?Where was Hydrotherosaurus found?

Its fossils were found in California, USA, in the Moreno Formation of Fresno County.1 2

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For dino experts

Scientific name: Hydrotherosaurus
Named by: Welles 19432
Group: Plesiosaurs
Family / clade: Elasmosauridae2
Classification: Plesiosauria > Elasmosauridae > Sauropterygia2
Age of the rocks: 72 to 66 million years (Maastrichtian)2
Rock formations: Moreno2
Countries: USA2
Fossil records: 1 in the Paleobiology Database2
Discovery: The first fossils were found by Frank C. Paiva in the Panoche Hills of California in 1937. In 1943, paleontologist Samuel Paul Welles named the species Hydrotherosaurus alexandrae after Annie Montague Alexander.1
Still debated: Scientists are not sure exactly how Hydrotherosaurus used its extremely long neck while hunting.1

Where the facts come from

Hydrotherosaurus (en.wikipedia.org)
Hydrotherosaurus 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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