Apatosaurus was the heavy-built classic sauropod: long neck, long tail, pillar-like legs, and a body made for bulk more than elegance. It lived in the Late Jurassic of North America and was one of the giant plant-eaters sharing that world with other famous sauropods like Diplodocus and Brachiosaurus. Modern descriptions tend to emphasize that it was more robust than Diplodocus, with a thicker neck and a more massive overall frame.

This is also the dinosaur at the center of the old naming drama. For much of the 20th century, people were told that Brontosaurus was really just Apatosaurus. That was the standard view for over a hundred years, though more recent work has argued that Brontosaurus may deserve to be separate again. So when people of our generation grew up hearing “Brontosaurus isn’t real,” what they were really hearing was the older taxonomic judgment, not that the animal itself was imaginary.