Dino card No. 1874 of 2,027

Vallecillosaurus

Say it: val-ay-see-oh-SORE-us

Ate: MeatMosasaursLate CretaceousNot technically a dinosaur

Vallecillosaurus was a small marine lizard that swam in the warm seas of Mexico during the Late Cretaceous, about 94 to 89 million years ago. It was less than 1 meter (3.3 feet) long, so it was much smaller than most of its giant cousins. It was not a dinosaur, but a relative of the mosasaurs, which were fierce sea reptiles.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

94 to 90 million years ago3

Late Cretaceous

Fossils found in

Mexico, in the state of Nuevo León, from the Agua Nueva Formation.1 3

Food

Meat2

Length

up to 1 m1

less than 1 m (3.3 ft) long

When did it live?

Triassic

Jurassic

Cretaceous

252 million years ago20114566, the asteroid

How big was it?

How long was it?

as long as 2 house cats nose to tailas long as 6 bananas end to end

How big was Vallecillosaurus compared to YOU?

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cool stuff

Fun facts

Vallecillosaurus is known from a fossil that includes the back half of the body, most of the tail, and part of the left hip and leg. This helps scientists understand how it moved.3

It lived in the ocean, not on land. The fossil was found in limestone that formed in a shallow sea.3

Its name honors a person named Don Roberto, because the species name is donrobertoi.2

Scientists think it was a type of aigialosaur, a group of small, semi-aquatic lizards that are close to the ancestors of giant mosasaurs.1 2

The fossil was found in rocks that are between 93.9 and 89.8 million years old, during a time called the Turonian.2

AI-made picture of Vallecillosaurus — An AI-made picture of how Vallecillosaurus 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 might think Vallecillosaurus was a dinosaur because it lived long ago and had a long tail.

Truth: It was actually a marine lizard, a relative of mosasaurs, not a dinosaur. Dinosaurs lived on land and had different body features.1

For dino experts

Scientific name: Vallecillosaurus
Named by: Smith and Buchy 20083
Group: Mosasaurs
Family / clade: Mosasauroidea3
Classification: Mosasauroidea3
Age of the rocks: 94 to 90 million years (Turonian)3
Rock formations: Agua Nueva3
Countries: Mexico3
Fossil records: 1 in the Paleobiology Database3
Discovery: Vallecillosaurus was named by Krister T. Smith and Marie-Céline Buchy in 2008. The fossil was found in the Vallecillo area of Nuevo León, Mexico.3 1
Still debated: Scientists are not sure exactly what Vallecillosaurus ate or how it hunted, because the fossil does not include the skull or teeth.2

Where the facts come from

Vallecillosaurus (en.wikipedia.org)
PBDB Taxon (paleobiodb.org)
Vallecillosaurus 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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