The Brontosaurus, meaning “thunder lizard,” is one of the most recognizable sauropods—the group of enormous, long-necked, plant-eating dinosaurs. Named in 1879, its image has long been cemented in popular culture as the archetypal giant from the prehistoric world. This creature has fascinated the public for over a century, even as its scientific name became the subject of one of paleontology’s most enduring debates. The story of this dinosaur is an intersection of scientific discovery, fierce rivalry, and a recent taxonomic return.
Defining the Brontosaurus: Physical Characteristics
The Brontosaurus was a giant quadrupedal herbivore. The largest species, B. excelsus, is estimated to reach lengths of up to 75 feet (23 meters). This massive body was supported by four thick, sturdy legs, with weight estimates ranging between 15 and 20 short tons.
Its most striking feature was the long neck, composed of deeply bifurcated vertebrae, giving it a wide and robust structure. The neck contained an extensive system of air sacs, which helped keep its overall weight manageable. Trailing behind its bulky torso was a long, whip-like tail, likely used for defense. The skull was often misidentified, with museums mistakenly using the boxier skull of the Camarasaurus until the correct, elongated skull, similar to Apatosaurus, was assigned.
The Tale of Two Names: Why Brontosaurus Vanished and Returned
The original naming of Brontosaurus by Othniel Charles Marsh in 1879 occurred during the intense rivalry with Edward Drinker Cope, known as the “Bone Wars.” Marsh had named Apatosaurus in 1877 from a partial skeleton. When he found a more complete specimen in Wyoming, he named it Brontosaurus excelsus, believing the two finds represented separate genera.
In 1903, paleontologist Elmer Riggs argued that Brontosaurus was not distinct enough from Apatosaurus to warrant its own genus. Under scientific nomenclature rules, the older name, Apatosaurus, had priority, and Brontosaurus was formally declared a junior synonym. For over a century, the dinosaur was scientifically referred to as Apatosaurus excelsus.
The name was resurrected in 2015 following a study by Emanuel Tschopp and colleagues. Researchers compared 477 anatomical features across 81 diplodocid specimens. The analysis determined that differences in features like the shoulder blade, ankle bones, and the structure of the neck vertebrae were significant. These differences validated Brontosaurus as a distinct genus once again.
Life in the Jurassic Period: Diet and Habitat
The Brontosaurus lived during the Late Jurassic period, approximately 156 to 146 million years ago. Fossils are primarily recovered from the Morrison Formation, a vast stretch of sedimentary rock deposits across the western United States. This environment was characterized by a semi-arid climate with wet and dry seasons, featuring floodplains cut by large rivers.
As a massive herbivore, Brontosaurus relied on the diverse plant life of the Morrison Formation. Vegetation consisted of ferns, cycads, ginkgos, horsetails, and tall conifers, since flowering plants had not yet evolved. Its long neck allowed it to browse on high foliage, consuming the substantial volume of plant matter necessary to fuel its enormous body.
The Brontosaurus shared its habitat with other large dinosaurs, including the sauropods Diplodocus and Brachiosaurus, and the predatory theropod Allosaurus. Evidence suggests they may have traveled in herds, which offered protection against large carnivores. Their enormous size and powerful, whip-like tail were primary deterrents against predators.