Apatosaurus

A heavier relative

Apatosaurus was a massive, long-necked plant-eater built like a heavier version of Diplodocus, with much stockier leg bones and a thicker, more heavily built neck. It grew to roughly 22 meters, about 72 feet, long, likely making it one of the heaviest animals ever to walk on land. It walked on four thick, column-like legs and held its long tail off the ground rather than dragging it. Like its relatives, it had a small head and peg-like teeth suited to stripping leaves rather than chewing them.

Its world

Apatosaurus lived in the Late Jurassic, between about 155 and 143 million years ago, across what is now Wyoming, Colorado, Utah, Oklahoma, Montana, and New Mexico. Its bones come from the Morrison Formation, alongside 60 separate finds attributed to the genus. It shared this world with the sauropods Brontosaurus, Diplodocus, Brachiosaurus, and Camarasaurus, the plated Stegosaurus, and predators including Allosaurus, Ceratosaurus, and Torvosaurus.

A name shared with a neighbor

Marsh named Apatosaurus in 1877, two years before he named Brontosaurus. For most of the twentieth century, paleontologists treated the two as the same animal, with Apatosaurus as the valid name and Brontosaurus set aside as a synonym. A later study of sauropod skeletons argued the two were different enough to count as separate genera after all, placing them together in the small group Apatosaurinae. The debate has not fully settled, and some scientists still prefer treating Brontosaurus as part of Apatosaurus.