What is the difference between Brontosaurus and Apatosaurus?

They look very alike. Apatosaurus was heavier and sturdier, with a thicker neck that sat lower on its body. Brontosaurus was a little slimmer. Scientists tell them apart mostly by bones in the neck, back and shoulders.

Why did scientists stop calling it Brontosaurus?

In 1903 a scientist called Elmer Riggs said there weren't enough differences between Brontosaurus and Apatosaurus. Apatosaurus had been named first, so its name was kept and Brontosaurus was dropped, until 2015.

What does Brontosaurus mean?

Noble thunder lizard. O. C. Marsh gave it the name Brontosaurus excelsus in 1879.

Big dinosaur questions

Is Brontosaurus real?

Yes! Brontosaurus is real. But for more than 100 years, scientists said it wasn't, and some older books and websites still say so.

Here's the whole story, and how to tell a Brontosaurus from its look-alike cousin, Apatosaurus.

An old painting of Brontosaurus wading in a swamp, with another long-necked dinosaur on the bank behind — Charles R. Knight painted Brontosaurus wading in a swamp in 1897. Elmer Riggs, the scientist who later took its name away, was one of the first to say these giants lived on land.

The short answer

Yes, Brontosaurus is real. A big study in 2015 showed it was its own dinosaur after all.
It isn't an Apatosaurus. Katia says it in Dinosaurs Are Back: “You might also hear it called Brontosaurus, but they're actually two different dinosaurs.”
Brontosaurus means “noble thunder lizard”. It lived about 156 to 145 million years ago, in what is now the USA.

From the last page of the book

What Katia says

Apatosaurus was a giant dinosaur that could grow up to 23 meters (75 feet) long! It took several years to grow that big. You might also hear it called Brontosaurus, but they're actually two different dinosaurs.

That's her fact about Apatosaurus, one of the ten dinosaurs Spike meets in Dinosaurs Are Back. Apatosaurus facts for kids

Why do people love the name so much?

Brontosaurus is easy to say and easy to remember. And, as a scientist at the Natural History Museum in London asked, “who wouldn't like the idea of a ‘thunder lizard’?”

1877 to 2015

Why people said it wasn't real

Brontosaurus and Apatosaurus were found in the late 1800s, during the “Bone Wars”, when two American fossil hunters, Othniel Charles Marsh and Edward Drinker Cope, raced to find and name the most dinosaurs.

1877
Apatosaurus gets its name
Marsh names a giant long-necked dinosaur found in Colorado: Apatosaurus.
1879
Brontosaurus gets its name
Two years later, a bigger, more complete skeleton turns up in Wyoming. Marsh calls it Brontosaurus, “noble thunder lizard”.
1903
Brontosaurus disappears
Elmer Riggs says the two aren't different enough. Apatosaurus was named first, so that name stays and Brontosaurus is dropped.
2015
Brontosaurus is back!
Scientists compare 81 fossils and 477 features of their bones, and find that Brontosaurus and Apatosaurus were different dinosaurs after all.

An old engraving of a Brontosaurus skeleton, side on, with a long neck and a long tail — Marsh's drawing of the Brontosaurus skeleton, from 1896.

Spot the difference

How to tell Brontosaurus and Apatosaurus apart

Apatosaurus

Heavier and sturdier
A thicker neck that sat lower on its body
Up to 23 meters (75 feet) long

Brontosaurus

A little slimmer
A thinner neck that sat a bit higher
Found in Wyoming, in the same rocks as Apatosaurus

They really do look VERY alike, so scientists tell them apart mostly by bones in the neck, the back and the shoulders.

3D Apatosaurus from Dinosaurs Are Back, ready to stand in your room in augmented reality

Drag to spin. On a phone or tablet this opens AR.

This is Apatosaurus, Brontosaurus's heavier cousin, from Dinosaurs Are Back. On a phone or tablet, tap “See it in your room”.

Is Brontosaurus the same as Brachiosaurus?

No! Both were long-necked plant-eaters that lived at the same time, but Brachiosaurus means “arm lizard”. Its front legs were longer than its back legs. That tilted its body up, a bit like a giraffe. Brachiosaurus facts

Questions kids ask

Quick answers

Is Brontosaurus real?: Yes. For more than 100 years scientists thought Brontosaurus and Apatosaurus were the same dinosaur, but a big study in 2015 found they were different, so Brontosaurus got its name back.
What is the difference between Brontosaurus and Apatosaurus?: They look very alike. Apatosaurus was heavier and sturdier, with a thicker neck that sat lower on its body. Brontosaurus was a little slimmer. Scientists tell them apart mostly by bones in the neck, back and shoulders.
Why did scientists stop calling it Brontosaurus?: In 1903 a scientist called Elmer Riggs said there weren't enough differences between Brontosaurus and Apatosaurus. Apatosaurus had been named first, so its name was kept and Brontosaurus was dropped, until 2015.
What does Brontosaurus mean?: Noble thunder lizard. O. C. Marsh gave it the name Brontosaurus excelsus in 1879.
Is Brontosaurus the same as Brachiosaurus?: No. Both were long-necked plant-eaters, but Brachiosaurus had front legs longer than its back legs, so its body tilted up like a giraffe's.

Keep asking

Dinosaurs Are Back

Spike's big adventure, with a giant Apatosaurus who has a thing for pineapples, and nine more dinosaurs that step off the page with a phone or tablet.

Buy on Amazon · $14.99 Look inside

Where these facts come from

Katia's facts are from the last page of Dinosaurs Are Back. Everything else was checked on these pages on September 27, 2026.

Natural History Museum, London: Brontosaurus, reinstating a prehistoric icon: 1877, 1879, 1903, the 2015 study, the differences, when and where it lived
Natural History Museum, London: Brachiosaurus

Picture credits

Brontosaurus painting, 1897: Charles R. Knight, via Wikimedia Commons, public domain.
Brontosaurus skeleton drawing, 1896: Othniel Charles Marsh, via Wikimedia Commons, public domain.