Brachiosaurus: Facts About the Giraffe-like Dinosaur

Brachiosaurus was an unusual dinosaur. Specimens have been found primarily in the fossil-rich Morrison Formation in North America, but it did not resemble any of the other dinosaurs that roamed the region. Its long neck made it look like a giraffe, and its forelegs were longer than its hind legs. The name Brachiosaurus, in fact, means "arm lizard."

Brachiosaurus lived 156 million to 145 million years ago during the mid- to late-Jurassic Period. It is not completely clear whether the Brachiosaurus was a warm- or cold-blooded animal. Many scientists believe that it was a gigantotherm — somewhere in between the warm- and cold-blooded animals of today, with a metabolism that was high compared to a reptile but slow compared to mammals.

At 40 feet to 50 feet (12 meters to 16 meters) tall, Brachiosaurus was among the tallest dinosaurs. It was about 85 feet (26 meters) long from head to tail. At the time of its discovery in 1903, Brachiosaurus was declared the largest dinosaur ever, but other sauropods, such as its close relative Giraffatitan, are now believed to have been a few couple meters taller than Brachiosaurus. Other brachiosaurids, including Argentinosaurus and Supersaurus, were also thought to be heavier than Brachiosaurus, which weighed about 25 tons (22.7 tonnes).

The dinosaur's skull had a wide muzzle and thick jaw bones that housed a total of 52 spoon–shaped teeth — 26 in each jaw — which were perfectly suited for stripping vegetation.

At first, paleontologists believed that Brachiosaurus lived mostly in the water due to its nostrils being at the top of its egg-shaped head. But scientists now believe that its deep, narrow body and relatively small footprint were not suitable for aquatic living.

In contrast to most other sauropods, Brachiosaurus had a sharply inclined back to accommodate its long forelimbs. Paleontologists believe that its neck, which was about 30 feet (10 meters) long, exited its body in a fairly straight line, resulting in it pointing upwards. The exact angle of its neck continues to be debated, as does its flexibility and mobility.

Paleontologists also debate whether Brachiosaurus kept its head raised continually or just when the herbivore dinosaur was foraging for food. A very large muscular heart would have been needed to raise its head to its full vertical height off the ground (40 feet, 12 meters), so some scientists believe that it held its head in a horizontal position much of the time when not in search of food in higher places.

Unlike its portrayal in the movie "Jurassic Park," paleontologists do not believe that Brachiosaurus could rear up on its slender, columnar hind legs. Because of its physical makeup, such a posture would not have given this herbivore much more access to food and it did not have any natural enemies that it had to intimidate. While there were plenty of known meat-eating dinosaurs — including Allosaurus, Ceratosaurus and Torvosaurus — that were close by, they were about half the size of Brachiosaurus and the carnivorous dinosaur most likely focused on smaller and easier prey.

What did Brachiosaurus eat?

Brachiosaurus fed on coniferous trees, gingkoes and cycads. An adult Brachiosaurus likely had to eat up to 400 lbs. (181 kilograms) of leafy greens daily to maintain its weight.

While it is believed that they stripped trees of their vegetation, it is likely that they supplemented their diets with vegetation at lower levels, especially as the food supply dwindled. Brachiosauruses are thought to have traveled in herds, moving on after they had exhausted the vegetation in a particular area.

Scientists believe that Brachiosaurus swallowed vegetation whole, as its teeth were suited to stripping vegetation but not breaking up large chunks of plants.

Fossil finds

The first Brachiosaurus fossil was found in Grand River Valley in western Colorado in 1900. The paleontologist who discovered this partial skeleton, Elmer Riggs, named this new find Brachiosaurus in 1903.

Brachiosaurus is one of the rarer sauropods of the Morrison Formation. Because the skull of the Brachiosaurus had a very tenuous attachment to the rest of its body and was easily detached after its death, there is only one skull that has been identified. In 1998, experts finally identified a skull unearthed by Othniel C. Marsh as definitively belonging to Brachiosaurus, rather than Apatosaurus.

In addition to North America, remains of the giraffe-like dinosaur have been discovered in Tanzania. Since Africa and North America were connected as part of a large super-continent at the time, Brachiosaurus had a huge range and possibly even roamed modern-day Europe.

The identification of Brachiosaurus remains is complicated by its close resemblance to the Giraffatitan ("giant giraffe"), which was native to northern Africa. Paleontologists are on the fence as to whether Giraffatitan merits its own genus or was a species of Brachiosaurus referred to as Brachiosaurus brancai.

Related:

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• Ankylosaurus: Facts About the Armored Dinosaur
• Apatosaurus: Facts About the 'Deceptive Lizard'
• Archaeopteryx: Facts About the Transitional Fossil
• Diplodocus: Facts About the Longest Dinosaur
• Giganotosaurus: Facts About the 'Giant Southern Lizard'
• Pterodactyl, Pteranodon & Other Flying 'Dinosaurs'
• Spinosaurus: The Largest Carnivorous Dinosaur
• Stegosaurus: Bony Plates & Tiny Brain
• Triceratops: Facts About the Three-Horned Dinosaur
• Tyrannosaurus Rex: Facts About T. Rex, King of the Dinosaurs
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