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Name means: Arm Reptile


Species: altithorax

Range: Late Jurassic (Tithonian, 150-145 MYA) from Utah, Wyoming, Colorado, and Oklahoma, possibly from Germany, Tanzania, and Zimbabwe

Size estimate: 85 ft length, 62 tons

Discovery: Elmer Riggs, 1903

Classification: dinosauria, saurischia, sauropoda, macronaria, brachiosauridae


Although Brachiosaurus ranks among the most popular dinosaurs, science knows surprisingly little about it. Most of what we know about its appearance comes from its African cousin Giraffatitan brancai. Giraffatitan looks so much like Brachiosaurus that scientists used to call it Brachiosaurus brancai. The real Brachiosaurus has a longer torso, shorter arms, and a heavier build than Giraffatitan. Its skull and much of its neck remains unknown, and its fossils rarely turn up in its home range: the Morrison Formation.


Its scarce remains have led to much debate about how to reconstruct it. Scientists continue to argue how its neck functioned, its metabolism, and its role in its ecology. We do know that it browsed from trees, and could reach higher than some of the other dinosaurs in its environment. Its long arms angled its neck toward higher branches, and its spoon-shaped teeth worked best on twigs and rough foliage. We also know that the dramatic scene in Jurassic Park where it reared up on its hind legs was physically impossible. Those long arms made its center of gravity too high for it to balance while on its hind feet.

What’s with the Fuzz?!

You might have noticed the spikes lining the back and hips of the Brachiosaurus. To a degree, they might resemble pictures you may have seen on the internet which add fuzz at random to dinosaurs. That’s not what these spikes represent. The only skin impressions we have for Brachiosaurus come from footprints, and they suggest it had small, spiky scales on its feet, sort of like soccer cleats. Scale impressions from other sauropods usually preserve a mosaic of large hexagonal scales. ­Diplodocus had a loosely Iguana-like fringe of scales along its dorsal ridge. Nothing supports fuzz on sauropods.

What are these spikes doing here? They play only a practical role. Seagulls and other birds were fond of perching on this Brachiosaurus sculpture’s back. When we refreshed the paint job, we added the spikes to prevent them from perching up there and covering the new paint up with a “paint job” of their own. The paint on the fuzz is intended to make them seem as invisible as possible—hopefully you have to squint to see them!

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