Brachiosaurus vs Brontosaurus: 5 Key Differences Explained

Written by Hannah Ward
Updated: September 19, 2023
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Brachiosaurus and brontosaurus are both large herbivorous dinosaurs from the late Jurassic period.  They are often confused with one another. That’s an easy mistake; they are both characterized by their extremely long necks and small heads.  So, it is possible to tell them apart?  The answer is yes. There are actually quite a few key differences between them.

For a start, they have very different shapes and stances and one can make a sound louder than a cannon.  One is a solitary animal while the other is a herd animal.  Also, even though they are both incredibly large, one is clearly bigger than the other.  But which one is it?  Join us as we learn about these fascinating dinosaurs and discover all of their differences.

Comparing Brontosaurus vs Brachiosaurus

Alternative NameThunder lizardArm lizard
SizeHeight – 28 feet
Length – 72 to 85 feet
Weight – 33,000 pounds
Height – 40 feet
Length – 60 to 70 feet
Weight – up to 128,000 pounds
EraLate Jurassic – 157 to to 145 million years agoLate Jurassic – 161 to 145 million years ago
Body ShapeLong, thin neck, small head, heavy body, long whip-like tail.
Elephant like
Small head, extremely long neck, muscular tail.
Giraffe like
LimbsFront legs slightly shorter than hind legsFront legs larger and longer than hind legs
NareNo nareLarge nare over skull, between eyes
HabitatOpen plains and marshy areasOpen plains and forests
Social StructureSolitaryHerd animal
DietAte vegetation at ground levelHigh browser – ate from canopies of trees
PredatorsAdults – no predators
Juveniles – Allosaurus and Ceratosaurus
Likely only Allosaurus preyed on the young, injured, or weak

The 5 Key Differences Between Brachiosauruses and Brontosauruses

On the surface, brachiosaurus and brontosaurus seem like they’re very similar – they’re both large, tall herbivores – but there is far more to them than meets the eye.  Both were so large they had very few predators and both had long necks with small heads.  However, despite their similarities, there are still plenty of key differences which make it easy to distinguish the two.

Brachiosaurus vs Brontosaurus: Size

How Long Were Dinosaurs on Earth

Brachiosauruses and brontosauruses were amongst the longest and tallest dinosaurs ever


The main difference between brachiosauruses and brontosauruses is their size.  Although both are incredibly large dinosaurs in their own rights, the former is longer, while brachiosaurus was generally taller. Brontosauruses weighed up to 33,000 pounds and reached a maximum of 28 feet in height.  However, because of their long neck and tail, they reached incredible lengths of between 72 and 85 feet.

Brachiosauruses, although still long, had the edge with their height.  Brachiosauruses had a length of 60 to 70 feet, but stood 40 feet tall.  They were also much heavier and reached an impressive 128,000 pounds.  As a direct comparison, the average weight of an African bull elephant (the heaviest animal alive on Earth today) is 12,000 pounds.  This means that brachiosaurus weighed more than ten African elephants!

Brachiosaurus vs Brontosaurus: Limbs

Another major difference between brontosaurus and brachiosaurus is the length of their limbs.  Brachiosaurus had front legs which were longer than their hind legs while brontosaurus had front legs that were shorter than their hind legs.

Brachiosaurus vs Brontosaurus: Body Shape

Brontosaurus with Human

Brontosaurus didn’t have a neck as adapted to reach incredible heights.


As we’ve just explained, brachiosaurus was taller while brontosaurus was longer and the length of their front legs compared to their hind legs differed.  This means that they had a different body shape and stance.  As brachiosaurus had longer forelegs their body naturally sloped steeply downward, while brontosaurus naturally sloped slightly the opposite way, giving it a hunched appearance.  Although they both had long necks and disproportionately small heads, the length of their legs and the slope of their bodies also meant that they carried themselves differently.  Brachiosaurus carried their necks up with a slight “S” curve and had a muscular tail.  Brachiosauruses are often described as being “giraffe-like” in their shape.

On the other hand,  brontosaurus is described as being “elephant-shaped“.  Brontosaurus didn’t carry their neck anywhere near as high as brachiosaurus.  Instead, they carried their neck out in front of them, almost parallel with the ground.  Due to this, they needed an extremely long tail to counterbalance their long neck.  Their tail was long and thin, tapering down at the end to resemble a whip.  Scientists believe that brontosauruses were able to whip their tails and produce a crack of more than 200 decibels – louder than a cannon.

Brachiosaurus vs Brontosaurus: Nare

Brontosaurus vs Brachiosaurus - A pair of brachiosaurus dinosaurs


Nares are large nasal openings and – in the case of the brachiosaurus – are located on the top of their head and look like a large bump in front of their eyes.  Brontosauruses don’t have these large nares.  It is believed that the nares on brachiosaurus are located there because of the air sacs that were also located down the neck.  These air sacs were connected to the lung system and were present all the way down the underside of their neck.

Brachiosaurus vs Brontosaurus: Diet

Brachiosaurus and brontosaurus were both herbivores and ate a range of plants and vegetation.  However, their diet differs in where they ate it from.  Due to the physiological differences between the two dinosaurs, brachiosaurus was a high browser while brontosaurus ate at ground level.  The incredible height of brachiosaurus gave it the means to be able to eat from the high canopies of trees.  Therefore, brachiosaurus ate vegetation usually from 16 to 30 feet high.

Brachiosauruses were so tall they ate from trees at heights of 16 feet and upwards

©DariuszSankowski / pixabay – License

FAQ’s (Frequently Asked Questions)

Are brachiosaurus and brontosaurus from the same family group?

No, although they were both sauropods – a group of dinosaurs that are characterized by their long necks, small heads, long tails, and large legs and bodies – they are not from the same family group.  Brontosaurus was from the family Diplodocidae which included some of the longest sauropods to have ever walked the earth.  Meanwhile, brachiosaurus was from the family Brachiosauridae which were some of the tallest.

Did brachiosauruses and brontosauruses live alongside each other?

Yes, both brachiosaurus and brontosaurus lived in the same areas, particularly in what is now North America during the late Jurassic period.  As the exact years that they existed overlapped, it’s easy to assume that they lived alongside each other.

Were brachiosauruses and brontosauruses dangerous?

Despite their great sizes, both brachiosauruses and brontosauruses were relatively peaceful animals.  They were both giant herbivores and had very few predators which meant they didn’t need to get into fights with other animals.  Probably the most dangerous aspect was the incredibly long tail of the brontosaur which was long and thin and was swung with immense power.

Why were brachiosaurus and brontosaurus called arm lizard and thunder lizard?

Brachiosaurus earned the nickname “arm lizard” because their forelegs were longer than their hind legs.  Brontosaurus is called “thunder lizard” because brontosaurus means thunder lizard in Greek.

What was the lifespan of brachiosauruses and brontosauruses?

Both brachiosauruses and brontosauruses are estimated to have had a lifespan of around 100 years.

Were there any dinosaurs larger than brachiosaurus?

Sauropods are generally believed to be the largest and heaviest dinosaurs, and for a long time it was thought that brachiosaurus was the largest dinosaur to have ever existed.  However, titanosaurs such as Argentinosaurus are now thought to have surpassed brachiosaurus in size.

What Was the Tallest Dinosaur Ever?

While there’s no denying that the brachiosaurus and brontosaurus were massively tall dinosaurs with their towering necks, there is another terrestrial sauropod that takes the title of the tallest to have ever roamed Earth.

Partial fossils of this towering creature, found in Texas, Oklahoma, and Wyoming, indicate that the sauroposeidon could raise its head 54-59 feet (16.5-18 m) off the ground–the equivalent of six stories! The neck bone of this dinosaur is comparable to that of a chicken or ostrich bone–thin and honeycombed with small air cells. This enables the animal to stretch its neck long as it’s lighter and easier to lift. From the shoulder, the sauroposeidon would have been 20-23 feet tall and had a length of up to 112 feet from head to tail. 

Importantly, while this sauropod was probably the tallest, it was not the largest land dinosaur by total size and body mass. That title still currently goes to the Argentinosaurus. As discoveries continue to be made, who knows if these facts will change?

The photo featured at the top of this post is ©

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About the Author

Hannah is a writer at A-Z animals where her primary focus is on reptiles, marine life, mammals, and geography. Hannah has been writing and researching animals for four years alongside running her family farm. A resident of the UK, Hannah loves riding horses and creating short stories.

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