Brachiosaurus: One of the Largest Land Animals That Ever Lived

Brachiosaurus was one of the largest animals ever to walk on land. It lived during the Late Jurassic Period, about 154 to 150 million years ago. Its name means "arm lizard," because its front legs were longer than its back legs — unusual for a sauropod and one of the features that gave it its iconic posture. This guide covers what scientists know about Brachiosaurus, drawn from museum collections in Berlin, Chicago, and the major Jurassic-period rock formations of western North America.

Quick facts#

• Lived: Late Jurassic, about 154 to 150 million years ago
• Length: 70 to 85 feet (21 to 26 meters) head to tail
• Height: 30 to 40 feet (9 to 12 meters) — taller than a 3-story building
• Weight: 30 to 60 tons (60,000 to 120,000 pounds) — about the weight of 10 elephants
• Diet: Herbivore (plant-eater)
• Where found: Western North America (Colorado, Utah, Wyoming) and possibly Africa
• Defining features: Extremely long neck, front legs longer than back legs, head held high

What Brachiosaurus looked like#

A long-necked giant with a body like a massive ridge. The neck alone was about 30 feet long. The head held high — at the highest point, the top of the head was roughly 40 feet above the ground, the height of a 3- or 4-story building.

The unusual leg proportions#

Most sauropods (long-necked dinosaurs) had back legs slightly longer than their front legs, like a modern giraffe in reverse. Brachiosaurus was different — the front legs were noticeably longer than the back. This gave the body a sloping profile, rising from the tail toward the shoulders, with the neck rising even higher from there.

This posture is what put the head so high. A 30-foot neck on a sauropod with horizontal posture (like Diplodocus) keeps the head about 15 to 20 feet up. The same neck on Brachiosaurus, with the body angled up and the neck angled up further, reached 40 feet — high enough to feed from the tops of trees other herbivores could not touch.

The head and teeth#

Small head for the body size — about the size of a horse's head. Chisel-shaped teeth at the front, perfect for stripping leaves off branches. No back teeth for grinding — Brachiosaurus swallowed plants whole and probably used gastroliths (stones in the stomach) to grind food as it digested.

The tail#

Long and tapering, but relatively short for a sauropod. Diplodocus and other sauropods had whip-like tails. Brachiosaurus's tail was more counterweight than weapon.

What it ate#

Pure herbivore. Conifers, cycads, ferns, ginkgoes — the dominant plants of the Late Jurassic. The unique selling point of Brachiosaurus was access to high vegetation other herbivores could not reach. While Stegosaurus, Camptosaurus, and other ground-level herbivores worked through low and mid-level plants, Brachiosaurus fed on the tops of trees 30 to 40 feet up.

A 50-ton animal needs enormous amounts of food. Estimates suggest Brachiosaurus ate 400 to 800 pounds of plants per day. Most of the day was probably spent eating.

How it held its head: a long-running debate#

For most of the 20th century, sauropod necks were depicted reaching skyward like swan necks. Then in the 1990s, biomechanical studies suggested the necks were held more horizontally, because pumping blood 40 feet up to a head would require an enormous heart and dangerously high blood pressure.

The current consensus, supported by the American Museum of Natural History's sauropod research, is more nuanced:

• Brachiosaurus probably could raise its head to about 40 feet when it wanted to — for feeding from high vegetation or for display
• But it did not hold its head straight up all the time — that would have been physiologically taxing
• The neck spent most of the day at varying angles, with the head moving between 25 and 40 feet up depending on what it was doing

The bones of the neck vertebrae suggest a wide range of motion, consistent with this flexible posture.

Where Brachiosaurus fossils are found#

The most famous Brachiosaurus specimens come from the Morrison Formation, a Late Jurassic rock formation that stretches across Colorado, Utah, Wyoming, and South Dakota. This formation was a vast floodplain 150 million years ago and preserves a huge diversity of dinosaurs.

The most famous specimens:

• The Berlin specimen at the Museum für Naturkunde in Berlin, mounted at over 40 feet tall — actually a closely related species (Giraffatitan), but historically called Brachiosaurus
• The Field Museum specimen in Chicago, where a Brachiosaurus altithorax skeleton is mounted in the lobby

There is ongoing debate about whether the African specimens (Giraffatitan) are the same genus as the North American Brachiosaurus. Most paleontologists now treat them as separate genera, but the popular name "Brachiosaurus" often gets applied to both.

For Florida families: no Brachiosaurus fossils in Florida. The Late Jurassic preceded the geological formation of much of present-day Florida by tens of millions of years. Florida's local prehistoric fossils come from far later periods — see our Florida's prehistoric past.

How scientists know its size and behavior#

Sauropod paleontology is one of the harder branches of dinosaur science because the sheer size makes complete skeletons rare. Most of what we know comes from:

• Partial skeletons — Brachiosaurus is known mainly from a handful of partial specimens
• Bone microstructure — growth rates suggest it took 25 to 30 years to reach full size
• Comparative anatomy with related species — Giraffatitan in Africa is more completely known and fills in some gaps
• Trackways — sauropod footprints, common in Jurassic rocks, confirm group behavior and walking gaits
• Bone bed analysis — multiple sauropods found together suggest social behavior

For more on the methodology, see how do scientists know what dinosaurs looked like.

At a Jurassic Petting Zoo event#

The baby Brachiosaurus is one of the five puppets in our petting zoo (Basic). Even at baby scale, the long neck and tall posture are the defining features kids notice. The puppetry lets kids see how the neck moves, how the front legs are longer than the back, and how the head reaches for food the way an adult Brachiosaurus would have.

For schools and families curious about meeting our baby Brachiosaurus, see the experience page.

Frequently asked questions#

Was Brachiosaurus the biggest dinosaur?#

One of the biggest land animals ever, but not THE biggest dinosaur. Several other sauropods exceeded Brachiosaurus in length or weight:

• Argentinosaurus — possibly 100+ feet long, 80+ tons
• Patagotitan — about 120 feet long, 70 tons
• Sauroposeidon — neck possibly reaching 50 feet up

Brachiosaurus was at the upper end of dinosaur size, but a few sauropods exceeded it. Brachiosaurus was the tallest of the well-known sauropods.

Could Brachiosaurus stand on two legs?#

Almost certainly not. The body weight was too great for two-legged posture. Some sauropods may have reared up briefly to reach higher vegetation or in defense, but standing fully bipedal would have been mechanically impossible at 50 tons.

Did Brachiosaurus live in herds?#

Probably yes, especially as juveniles. Bone beds and trackways suggest group behavior, though adults may have been more solitary. The full social structure is debated.

What did baby Brachiosaurus look like?#

Like a small version of the adult — long neck, four legs, sloping back. Newly hatched Brachiosaurus were about 3 feet long. They grew rapidly during their first decade, then more slowly through their teens and twenties to reach full size at age 25 to 30.

Did Brachiosaurus have any predators?#

As an adult, almost nothing could hunt a 50-ton Brachiosaurus successfully. Juveniles, sick adults, and elderly individuals were more vulnerable. Allosaurus and other large Jurassic predators probably hunted them when opportunity allowed, but adult Brachiosaurus was essentially predator-proof through size alone.

When did Brachiosaurus go extinct?#

Brachiosaurus went extinct at the end of the Jurassic Period, about 150 million years ago — long before the asteroid impact that killed T-Rex and the other end-Cretaceous dinosaurs. The cause was probably environmental change: shifting climate and habitat as the supercontinent Pangaea continued to break up. Other sauropods (different species) continued through the Cretaceous in various forms.

See the giants of the Jurassic#

A Brachiosaurus skeleton at a museum is staggering — 40 feet of bone and you have to crane your neck to see the head. The baby version at a Jurassic Petting Zoo event lets kids actually touch and interact with the proportions that make sauropods special. For South Florida schools and families, see the experience page or check date availability for a date that works.