A brontosaurus was a massive plant-eating dinosaur that lived about 150 million years ago during the Jurassic Period. Picture an animal as long as two school buses, with a body like an elephant's but much larger, four thick legs like tree trunks, and a tremendously long neck stretching up to reach the highest leaves. Its tail was equally long, helping balance that enormous neck.

The name means “thunder lizard” because people imagined the ground shaking when these giants walked. Scientists first discovered brontosaurus fossils in the American West in the 1870s, and the dinosaur quickly became one of the most famous prehistoric creatures, appearing in museums, books, and movies.

Here's something fascinating: for over a century, scientists argued that brontosaurus was actually the same dinosaur as another species called apatosaurus. Museums even had to change their labels. But in 2015, after carefully studying dozens of skeletons, researchers concluded that brontosaurus really was its own distinct type of dinosaur after all. In a way, the brontosaurus had been “extinct” twice: once 150 million years ago when the actual animals died out, and once in 1903 when scientists mistakenly decided it didn't exist as a separate species.

Today, the brontosaurus remains a symbol of the Age of Dinosaurs, reminding us how truly enormous some prehistoric creatures were.