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Brachiosaurus, Late JurassicMorrison Formation, Colorado · named 1903
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Brachiosaurus

BRAK-ee-oh-SORE-us

"arm lizard"

Type species Brachiosaurus altithorax

Lived
155 to 143 million years ago, Late Jurassic
Diet
Herbivore
Length
about 21 m (69 ft)
Group
Sauropods, Brachiosauridae
Found in
United States
Named by
Riggs 1903

Size comparison

To scale

Where its fossils were found

The evidence

Today

11 finds

150 million years ago

Map: C. R. Scotese, PALEOMAP

Also reported from Zimbabwe.

Habitat

Rivers crossed broad floodplains in the Morrison Formation landscape, where conifers, ferns and horsetails grew. Stegosaurus, Camptosaurus and Brontosaurus shared this world.

Field notes

About Brachiosaurus

What it was like

Brachiosaurus was a giant plant eater with a long neck and a small head. Unlike most sauropods, its front legs were longer than its back legs, which gave its back a steep, sloped shape. It grew up to about 21 meters (69 feet) long.

Its long neck let it reach leaves high up in trees that shorter plant eaters could not touch. Brachiosaurus was not built for rearing up on its hind legs the way some other sauropods may have been.

Its world

Brachiosaurus lived from about 155 to 143 million years ago, spanning the Late Jurassic and Early Cretaceous, in what is now the western United States, with possible fossils also reported from Zimbabwe. Its bones come from the Morrison Formation, alongside Stegosaurus, Allosaurus, Diplodocus, and Apatosaurus.

How it was found

Riggs named Brachiosaurus in 1903, choosing a name that means arm lizard for its long forelimbs. Only about 11 fossil finds of the genus are known, so it remains one of the rarer sauropods of its time and place, and much about its life is still uncertain.

Field gallery

More views of Brachiosaurus

Scenes reconstructed from the available fossil evidence.

Brachiosaurus in its habitat, photo 1

1 of 7

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 Brachiosaurus.

The evidence

The science behind Brachiosaurus

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

From its own fossils

  • The original partial skeleton preserves trunk vertebrae, ribs, hip bones and large limb bones.
  • Its long upper arm bones support a high-shouldered body with forelimbs longer than the hindlimbs.

Borrowed from relatives

  • Giraffatitan and other brachiosaurids help fill gaps in the neck, skull and feet.
  • Scaly skin is inferred from skin preserved in other sauropods.

Still unknown

  • The exact outline of its head and the soft tissues around its nose.
  • Whether the small juvenile brachiosaurid skeleton belongs to Brachiosaurus or a close relative.
  • Its color and whether it traveled in herds.

Often drawn wrong

  • Many familiar reconstructions borrow the head and body of Giraffatitan, which is a separate genus.
  • Its compact front feet were weight-bearing columns, rather than elephant feet with a row of exposed toenails.

Discovery timeline

  1. 1903Named itRiggs
  2. 2001SkullWitmer
  3. 2009Full descriptionTaylor
  4. 2012Growing upCARBALLIDO et al.
  5. 2019SkullD'Emic & Carrano

Key papers

The research behind what we know of Brachiosaurus

Close relatives

Other members of Brachiosauridae

Sources: Wikidata