Brachiosaurus: the giraffe-shouldered Jurassic colossus

When and where

Brachiosaurus lived during the Late Jurassic, roughly 154 to 150 million years ago, in what is now western Colorado. The type specimen came out of the Morrison Formation, the same fossil-rich layer that produced Diplodocus, Allosaurus, and Stegosaurus, but Brachiosaurus is rarer than any of them. Most of what is known about the genus comes from a small handful of partial skeletons and isolated bones found between Colorado and Utah, in floodplain sediments laid down beside seasonal rivers and lakes.

How we know

Elmer S. Riggs of the Field Museum named Brachiosaurus altithorax in 1903, working from a partial skeleton found at Riggs Hill near Grand Junction, Colorado in 1900. The generic name means "arm lizard," referring to the forelimbs being longer than the hindlimbs. African specimens originally classified as Brachiosaurus brancai were reassigned to a separate genus, Giraffatitan, in 2009, after a careful skull-and-vertebra comparison showed they belonged to a different family branch. The mounted skeleton on display at Chicago's Field Museum is a composite, since no single complete Brachiosaurus has ever been recovered. Source: Wikipedia entry on Brachiosaurus.

What set it apart

The forelimb proportions changed how the animal lived. With shoulders towering above the hips, Brachiosaurus held its neck closer to vertical than most sauropods, reaching feeding height of around 9 metres without rearing. The chest was deep, the tail short for a sauropod, and the nostrils sat high on a domed forehead, leading to long-running debates about whether the animal was semi-aquatic, fully terrestrial, or a high browser. Modern bone-density analysis from the 2010s settled the debate: Brachiosaurus walked on land. Length estimates put the animal at 22 to 23 metres. Weight estimates remain wide, between 30 and 58 tonnes depending on the modelling method, with most recent papers landing near 40 tonnes.

For collectors and classrooms

A scaled Brachiosaurus figurine shows the proportions that make the genus distinctive: shoulders higher than hips, neck angled upward, tail short. Avoid models that force a horizontal neck, since those copy older Apatosaurus poses. Browse a hand-painted figurine.