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.