This entry is part 2 of 3 in the series Dinosaur Theme Week

Apatosaurus vs. Brontosaurus

Scientists have definitively identified more than 300 genera and more than 700 species of dinosaurs. These numbers seem surprisingly low; the real total is likely much higher, as we have to dig through hundreds of millions of years of rock for a shot at finding fossilized dino bones.

Ask many toddlers, however, and the number of dinosaurs is around four: T. RexStegosaurusTriceratops, and Brontosaurus. The more enterprising dinosaur enthusiasts among our youth might be able to add Velociraptors if they’ve seen the Jurassic Park films or Pterodactyls. Some might scold you for confusing the Brontosaurus with the larger Brachiosaurus.

You might be excused for mixing up the sauropods, huge dinosaurs with long necks and tails. Many of their representations look similar. Up to 72 feet long, researchers believed Brachiosaurus to be the largest dinosaur ever to have lived when it was discovered in 1903. In Jurassic Park, the sauropod we see is a Brachiosaur.

Despite the inclusion in the most famous film about dinosaurs, Brachiosaurus isn’t the first sauropod most children learn. Show my daughter a long-necked dino and she’ll tell you it’s a Brontosaurus.

If you’re like me, you might read the preceding paragraphs and shout every time the word Brontosaurus is typed. I distinctly recall, at some point in my early dinosaur studies, learning that my favorite long-necked dino didn’t exist. What I thought was a Brontosaurus was actually an Apatosaurus.

As a child, I never truly comprehended the story, but I came to understand that Brontosaurus was fake and the sauropod toys with which I played represented Apatosaurus, a scientifically accurate, real-deal dinosaur.

Even knowing this tidbit, most people continued to call them Brontosaurs. It was just a better name.

An Apatosaurus skeleton at the Carnegie Museum - photo by Tadek Kurpaski

What caused this odd kerfluffle between a dinosaur that walked the Earth and one that might be a fabrication? As it turns out, the confusion over the two dinosaurs long predates my fascination as a child, and the names might be a big reason for the perplexity.

The issue began in the 19th century with one of the greatest early fossil hunters, Othniel Marsh (great name). In 1877, Marsh and his team uncovered a massive sauropod in Colorado. They named it Apatosaurus ajax. Apatosaurus comes from combining the Greek words apatē and sauros, which mean “deceptive” and “lizard.” This Deceptive Lizard featured some bones unlike most other dinosaurs, which puzzled the scientists, leading to the name. Ajax was one of the biggest, mightiest Greek heroes, so it seemed a fitting second half.

Two years later, in Wyoming, Marsh’s teams discovered another sauropod. This specimen was much larger than the Apatosaurus from Colorado, so they figured they had a new genus on their hands. They christened this one Brontosaurus excelsus. It was so large that it must have made the ground thunder as it walked, so Marsh named it brontē (thunder) + sauros (lizard). Excelsus translates to “noble.”

Noble Thunder Lizard conjures a brighter image than Deceptive Lizard, and Brontosaurus rolls off the tongue more sublimely than Apatosaurus. Is that ah-pat-o-saur-us or ah-pot-o-saur-us? At the time, few paid attention, as the dinosaurs weren’t competing for the attention of children, they were just two dead types of distantly related critters.

Marsh's 1896 sketch of Brontosaurus excelsus

Fast forward to 1903. Marsh had died. Another dinosaur expert, Elmer Riggs, the first paleontologist at Chicago’s Field Museum, began to study sauropods. One of his assistants unearthed the first Brachiosaurus in Colorado. Riggs compared many of the known specimens of Apatosaurus and Brontosaurus and argued that not enough differences existed between them for the dinos to occupy two distinct genera. Before Riggs, the dinos were as different as a domestic cat and a lion, for example, both felines but with a decent amount of evolution between them. After Riggs, scientists viewed them as akin to the difference between lions and tigers, members of the same genus.

If we should classify the two as the same genus, we have a naming problem on our hands. And the conventions of scientific naming were clear: when a reclassification produced a redundancy or a discrepancy, the tie went to the name that existed first.

So, Brontosaurus excelsus became Apatosaurus exclesus.

The dino that produced the name Brontosaurus did exist, but the name Brontosaurus had to go.

Elmer Riggs on the left, excavating a mastodon in Argentina - Field Museum Library

In the zeitgeist, however, the name would not disappear.

People simply stuck to Brontosaurus, probably because Thunder Lizard is a much better moniker than Deceptive Lizard. Despite no scientists utilizing the nomenclature throughout the 20th century, most people learned Brontosaurus when they discovered sauropods. Perhaps a child heard whispers of the Apatosaurus confusion, diving into dinosaur books, but few people had paleontologists around to correct any mistakes.

The 1925 silent film version of The Lost World (Conan Doyle’s, not Jurassic Park II) contained a Brontosaurus. The famous Sinclair Motor Oil mascot – a sauropod – was created in 1930. DINO, as it was affectionately known, was a Brontosaurus to the company. 1933’s King Kong included a rampaging, human-eating Brontosaurus. The gall of Merian C. Cooper and Ernest B. Schoedsack to include such scientific inaccuracy in a film about a gargantuan gorilla is astounding. That should have been a human-eating Apatosaurus!

The Sinclair Oil Corporation logo

Perhaps the genesis of my era’s knowledge of the Apato-Bronto mess was the U.S. Postal Service’s foray into the fray in 1989. They issued dinosaur stamps that year, including one of Brontosaurus. Some criticized the government for “fostering scientific illiteracy.” The Postal Service rebutted with, “Although now recognized by the scientific community as Apatosaurus, the name Brontosaurus was used for the stamp because it is more familiar to the general population.”

Still, throughout the 20th century, paleontologists regarded Brontosaurus as a synonym for Apatosaurus, designating the latter as the proper classification.

So, it seemed Brontosaurus was, in fact, wrong. 

[insert record scratch sound effect]

But hold onto your prehistoric horses.

In 2015, the Brontosaurus said, “Don’t call it a comeback, I’ve been here for hundreds of millions of years.”

Science is all about evolution, and not just going from dinosaurs to birds. As technology and knowledge increase, sometimes ideas must evolve. A group of researchers studied the skeletons of nearly 100 Apatosaurs and Brontosaurs, probing almost 500 anatomical characteristics. A century of expertise and a greater sample size prompted them to revisit the debate. This inquiry noted as many differences between the two as in other genera classified as distinct. Further, they include more dissimilarities than many species of a single genus. Their verdict: Brontosaurus should be distinct from Apatosaurus!

Not everyone is convinced, however. Some scientists believe the number of specimens involved is not enough to indicate a universal distinction. Others aver the differences to be subjective, thinking another set of criteria might show them to be single-genus worthy. Another grouping finds the study persuasive but is willing to swing toward one genus if new evidence comes from underground. Such is the way of science.

Is Brontosaurus back? We’ll give the official Mountains Are Calling stamp of “yes.” At the very least, I now understand one of the biggest mysteries of my childhood and I can speak with some authority to my children when they see sauropods. Noble Thunder Lizard is a terrific name, better than Deceptive Lizard and much superior to Arm Lizard, the translation of Brachiosaurus.

Now, if we can do for Pluto what we’ve done for Brontosaurus, the solar system will be a much better place.

Further Reading and Exploration

Brontosaurus: reinstating a prehistoric icon – The Natural History Museum, London

Brontosaurus or Apatosaurus? – American Museum of Natural History (pre-2015 article!)

DINO History – Sinclair

A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda) – Tschopp, Mateus, and Benson in PeerJ

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