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Rocasaurus, Late CretaceousAllen Formation, Argentina · named 2000
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Rocasaurus

"Roca lizard"

Lived
72 to 66 million years ago, Late Cretaceous
Diet
Herbivore
Group
Sauropods, Saltasauridae
Found in
Argentina
Named by
Salgado and Azpilicueta 2000

Where its fossils were found

The evidence

Today

2 finds

70 million years ago

Map: C. R. Scotese, PALEOMAP

Habitat

Rocasaurus lived in what is now Argentina, where the Allen Formation preserves a rich community of plant eaters. Other dinosaurs from these rocks include Aeolosaurus, Austroraptor and Patagopelta.

Field notes

About Rocasaurus

What it was like

Rocasaurus was a small titanosaur, a long-necked plant eater related to Saltasaurus. It is known from bones of the backbone, hips and legs.

Its world

It lived about 72 to 66 million years ago, at the end of the Late Cretaceous, in what is now Argentina. Its bones come from the Allen Formation, where it shared the land with the raptor Austroraptor, the titanosaur Aeolosaurus and the armored Patagopelta.

How it was found

Salgado and Azpilicueta named it in 2000. It is named after a nearby town.

Field gallery

More views of Rocasaurus

Scenes reconstructed from the available fossil evidence.

Rocasaurus in its habitat, photo 1

1 of 3

Lived alongside

Found in the same rock formations

A rock formation can hold fossils laid down millions of years apart, so not every animal here met Rocasaurus.

The evidence

The science behind Rocasaurus

Which parts of the picture come from its own bones, and which come from its relatives.

From its own fossils

  • The original partial skeleton includes neck, back and tail vertebrae, hip bones and a straight, moderately stout thigh bone.
  • Its tail vertebrae contain internal air spaces, extending far along the tail.
  • Deep hollows beneath the tail vertebrae are divided by a thin lengthwise wall of bone, a feature used to identify more of its tail bones from the same rocks.

Borrowed from relatives

  • The missing arms and lower legs are restored by comparison with Saltasaurus and Neuquensaurus.
  • The missing skull is restored by comparison with Tapuiasaurus, a titanosaur known from a well-preserved skull.

Still unknown

  • Its skull, arms, lower legs, hands and feet, and its adult body proportions.
  • Whether it carried the same arrangement of bony skin armor as Saltasaurus.
  • Its color and exact diet.

Discovery timeline

  1. 2000Named itSalgado & Azpilicueta
  2. 2011RedescriptionGarcia & Salgado
  3. 2012Full descriptionCerda, Salgado & Powell
  4. 2025New findFernández, Windholz & Zurriaguz
  5. 2026Inside the bonesFernández, Zurriaguz & Windholz

Key papers

The research behind what we know of Rocasaurus

Close relatives

Other members of Saltasauridae

Sources: Wikidata