Which dinosaur is commonly known as the 'thunder lizard'?

The dinosaur commonly known as the “thunder lizard” is Brontosaurus. The name combines the Greek words brontē, meaning “thunder,” and sauros, meaning “lizard.”

Brontosaurus was a long-necked sauropod that lived during the Late Jurassic, roughly 157–145 million years ago, in what is now the western United States. It belonged to a group of enormous plant-eating dinosaurs with pillar-like legs and long tails.

The name has a complicated history. Othniel Charles Marsh named Brontosaurus excelsus in 1879, but later researchers concluded that its fossils belonged to the genus Apatosaurus. For much of the 20th century, Brontosaurus was treated as an outdated name. A 2015 study argued that Brontosaurus was distinct enough to be restored as a valid genus, although scientists continue to debate parts of its classification.

A common mix-up is confusing Brontosaurus with Brachiosaurus or Diplodocus. All were sauropods, but they were different genera with different body proportions and evolutionary histories.