Brontosaurus: The dinosaur that was discovered twice
Few dinosaurs have had such a checkered history as the Brontosaurus. For almost the entire 20th century, experts claimed that this name didn't exist, that it was simply another name for Apatosaurus. Nevertheless, children learned the name Brontosaurus in school, generation after generation. Then, in 2015, came the surprise: a major study proved them right. Brontosaurus is its own genus.
At a glance
| feature | Value |
|---|---|
| length | approx. 22–26 m (values vary depending on the species) |
| Weight | approx. 15–32 t (values vary depending on the species) |
| Location | Morrison Formation, especially Como Bluff in Wyoming, USA |
| age | Late Jurassic, approximately 155–145 million years ago |
| Food | herbivores |
| group | Sauropoda, family Diplodocidae |
Weighing up to 32 tons, Brontosaurus was as heavy as five large elephants combined. Even the smaller specimens were 22 to 26 meters long. That's as long as two articulated buses end to end. The wide range in size and weight has a simple explanation: the name Brontosaurus currently refers to three different species of varying sizes.
A discovery in the middle of the race for bones
The discovery of the Brontosaurus is owed to a fierce dispute. In the 1870s and 1880s, the so-called "Bone Wars" raged. Two fossil hunters competed to find bones in the western United States. Their names: Othniel Charles Marsh and Edward Drinker Cope. Due to time constraints, both often described their finds rather briefly and hastily.
In 1879, Marsh discovered a skeleton near Como Bluff in Wyoming. He gave it a new name: Brontosaurus excelsus, the "sublime thunder lizard." Two years later, a more detailed description of the nearly complete skeleton followed. Marsh highlighted one feature as particularly important: the sacrum consisted of five vertebrae, fused together. In similar genera, there were at most four.
How the name suddenly disappeared
In 1903, a team led by Elmer Riggs from the Field Museum in Chicago examined a sauropod skeleton. Their conclusion: the previously separate genera were too similar. According to the rules of naming, in such a case the older name takes precedence. Apatosaurus had already been named in 1877, two years before Brontosaurus. Therefore, the younger name disappeared from scientific literature.
He had only disappeared from the realm of dinosaurs, not from people's minds. The name Brontosaurus remained present in schoolbooks and museums for decades. In 1989, the US Postal Service issued a series of dinosaur stamps. They chose "Brontosaurus" instead of the scientifically correct "Apatosaurus." The Smithsonian Museum complained. public: "Cartoon names instead of scientific names," was the accusation. Particularly ironic: The series was presented at Disney World, of all places.
2015: The major investigation brings about a change
A doctoral thesis changed everything. Researcher Emanuel Tschopp, at the University of Lisbon, compared all the fossils of the Diplodocidae. He collaborated with Octávio Mateus and Roger Benson from the University of Oxford. They examined 81 individual skeletons – not just individual species. To do this, they analyzed 477 physical characteristics – at the time, one of the largest studies of its kind on sauropods. Tschopp's initial goal wasn't to revive Brontosaurus. He was only interested in the relationships within the Diplodocidae.
The results were published in the journal in 2015. PeerJ and yet surprised everyone. Until then, the skeletons had been classified as Apatosaurus excelsus. But they differed from other Apatosaurus species in at least twelve important characteristics. Such a large number of differences is usually only found between long-established, independent genera. Diplodocus and Barosaurus are examples of this. A true Apatosaurus, therefore, had a significantly more robust neck than Brontosaurus. Conversely, Brontosaurus possessed its own distinctive features. These include a rounded bulge on the shoulder blade and different dimensions of an ankle bone.
The scientific community reacted largely positively. Researcher Paul Upchurch from University College London said he wanted to use the name again from now on. Philip Mannion from Imperial College London also welcomed the comeback. Brontosaurus has a firm place in the public imagination, he said. It's only good that it's back. Other experts urged caution. How many differences are sufficient to classify it as a separate genus is not always clear.
Three species under one name
The 2015 study assigned three species to the revived genus. Two of these had previously been known by their own names:
- Brontosaurus excelsus – the type species. Named in 1879 by Marsh, found at Como Bluff in Wyoming.
- Brontosaurus parvus – previously classified as its own genus Elosaurus, named in 1902.
- Brontosaurus yahnahpin – previously classified as its own genus Eobrontosaurus, named in 1994. According to the study, it is the oldest of the three species.
A body like a walking crane
Brontosaurus walked on four legs that resembled pillars. Its neck was extremely long, as was its whip-like tail. To date, no one has found a complete skull of the type species. This illustrates that even well-studied dinosaurs often remain incomplete. The animal could probably raise its tail and swing it sideways. Some researchers suggest it functioned as a whip for defense, but this has not been definitively proven.
Like other sauropods, Brontosaurus likely had air sacs in its vertebrae. This system is similar to that of modern birds. It made breathing easier in such a massive body.
Anyone comparing Brontosaurus and Brachiosaurus will immediately notice the difference in their legs. In Brontosaurus, the front and hind legs were roughly the same length, meaning its back was horizontal. Brachiosaurus, on the other hand, had significantly longer front legs. Its back sloped downwards, similar to a giraffe. The tail was also different: Brontosaurus's was longer and whip-like, while Brachiosaurus's was shorter.
What was on the menu?
Its head was small, tiny in relation to the rest of its body. Despite this, Brontosaurus could eat enormous quantities of plants. The reason: it didn't chew at all. Like a bird, it probably possessed a gizzard. It also swallowed stones that ground up its food. Some researchers suspect even more. The animal may have been able to stand on its hind legs at times. This would have allowed it to reach tall plants. This, too, is unproven – just a theory.
Not a swamp dweller
This old idea is now considered disproven: Brontosaurus was a purely land animal. Nevertheless, the notion persisted for a long time that giant sauropods like it spent most of their time half-submerged in swamps to support their weight. Its anatomy contradicts this: the column-like legs and the air sacs in its skeleton. This is how it carried its weight on land – much like a modern-day elephant.
The Diplodocoidea also include Amargasaurus from the Lower Cretaceous of Argentina.
More information on this topic can be found at urzeittiere.net
Brontosaurus lived at the same time as Camptosaurus, in the same Morrison Formation. Camptosaurus, however, was a significantly smaller herbivore with a completely different feeding strategy. Similarly, it also built Brachiosaurus – however, with significantly longer front legs than hind legs, as described above in the body structure comparison.
Image sources:
Size comparison: Matt Martyniuk, CC BY-SA 4.0, via Wikimedia Commons
Brontosaurus skeleton: Matthew Bellemare, CC BY-SA 2.0, via Wikimedia Commons