Home > Diorama > Dinosaur Explorer > Brontosaurus The Brontosaurus (which literally means "thunder lizard") is one of the largest known reptiles to have ever lived. Othniel Marsh first discovered its fossils in 1877 in a rock quarry. Brontosaurus is thought to have lived during the late Jurassic Period more than 140 million years ago. These herbivores (plant-eaters) got as long as 80 feet and weighed up to 33 tons. The Brontosaurus' long slender neck allowed it to feed on leaves near the tops of trees. In 1975, it was discovered that the Apatosaurus and Brontosaurus were in fact the same animal, and the name Brontosaurus was formally removed from all paleontology records. Eight Brontosauruses can be found in the diorama at Universe of Energy, and are located in the "marsh scene" directly in front of the vehicle holding area (where the Travelling Theater vehicles are still in "6-Pack" formation).