Brontosaurus

Lore & Background

The anatomy of Brontosaurus is well known, with fossils demonstrating that it was large, long-necked, and quadrupedal with a long tail terminating in a whip-like structure. The cervical vertebrae are notably extremely robust and heavily built. The forelimbs were short and stout whereas the hindlimbs were elongated and thick. The largest species B. excelsus reached up to 21–23 m from head to tail and weighed 15–20 t, whereas the smaller B. parvus only got up to 19 m long. Juvenile specimens are known, with younger individuals growing rapidly to adult size in as little as 15 years. Brontosaurus has been classified within the family Diplodocidae, in the subfamily Apatosaurinae, which includes only it and Apatosaurus.

Reader's Guide

Brontosaurus was a large, quadrupedal herbivore with a very long neck and a long tail that ended in a whip-like structure. Its neck vertebrae were notably thick and robust, contrasting with the lighter build of relatives like Diplodocus. The forelimbs were short and sturdy, while the hindlimbs were longer and thick, supported by heavy shoulder and hip bones. The largest species, B. excelsus, measured up to 21–23 meters in length and weighed 15–20 tonnes, while the smaller B. parvus reached only about 19 meters. Juvenile fossils show that young individuals grew to adult size in as little as 15 years. Brontosaurus belonged to the family Diplodocidae, a group of sauropods with shorter necks and longer tails than other families. Within this family, it is placed in the subfamily Apatosaurinae alongside Apatosaurus, both distinguished by their robust builds and thick necks. This subfamily was named in 1929 but was not used validly until a 2015 study that reinstated Brontosaurus as a distinct genus, though some paleontologists still consider it a synonym of Apatosaurus. Brontosaurus lived in the Morrison Formation of Utah and Wyoming around 156 to 146 million years ago. This formation hosted a rich ecosystem with over 16 sauropod genera, leading to niche partitioning among them. Brontosaurus shared its environment with other sauropods like Diplodocus, Barosaurus, and Brachiosaurus; ornithischians such as Stegosaurus, Dryosaurus, and Camptosaurus; and theropod predators including Allosaurus, Marshosaurus, and Ceratosaurus.

Did You Know?

• The name Brontosaurus means 'thunder lizard' from the Greek words for 'thunder' and 'lizard'.
• The type specimen of B. excelsus (YPM 1980) was one of the most complete sauropod skeletons known at the time of its discovery.
• The first mounted skeleton of a sauropod, unveiled in 1905 at the American Museum of Natural History, was referred to as Brontosaurus excelsus and used a sculpted skull based on Camarasaurus.
• A 2015 study by Emmanuel Tschopp and colleagues found Brontosaurus to be distinct from Apatosaurus, though some paleontologists still consider it a synonym.

Common Misconceptions (Editorial)

Some people think Brontosaurus was a fictional or invalid dinosaur for most of the 20th century, but the facts show it was simply considered a synonym of Apatosaurus until a 2015 study reestablished it as a distinct genus. Another common misconception is that no Brontosaurus skull was ever found; in fact, the early mounted skeleton used a sculpted skull based on Camarasaurus because no Brontosaurus skull was known at the time.

Why It Matters (Editorial)

Brontosaurus endures because it perfectly embodies the cultural image of the massive, gentle long-necked dinosaur—so much so that its name has outlasted decades of scientific controversy. Its comeback in 2015 also highlights how paleontology is a living science, where new evidence can overturn long-held conclusions and remind us that even “common knowledge” about extinct animals can change.