April 4, 2022 Scott Kraus

Brachiosaurus was a High Browsing Sauropod From the Late Jurassic

Brachiosaurus, pronounced “BRACK-ee-uh-Sawr-us”, was a large quadrapedal sauropod dinosaur. It was a herbivore from the late Jurassic period, living about 140-155 million years ago. The name Brachiosaurus comes from the Greek meaning “arm lizard”. It’s front limbs were quite long in relation to the rest of its body, kind of like arms. With those long limbs and its long neck, it shared an intriguing physical similarity with the modern-day giraffe. Because of that similarity, paleontologists suppose that Brachiosaurus probably was what they call a “high browser”, meaning they grazed from the leaves of tall trees like giraffes do.

Quick Facts

What did Brachiosaurus look like?

Brachiosaurus was an extremely large quadrapedal dinosaur, with a long neck and proportionately small head. In this way it was similar to other sauropods. However, it differed from other sauropods in a couple ways. It had longer forelimbs than hind limbs. In this way it was more like a modern giraffe. Also, although it had a long tail it was not as long as the tails of most sauropods. Brachiosaurus is one of the most recognizable dinosaurs among herbivores due to its very long neck and giant body.

Brachiosaurus Had An Unusually Long Neck

Brachiosaurus had a neck that could stretch up to about 30 feet. Twelve individual vertebrae supported it, with each vertebral bone measuring about three feet. The length was useful for reaching tall and leafy tree branches to graze on. Scientists aren’t in total agreement about how its heart could have supplied enough blood to the head if it was elevated so high above the rest of the body. Frequent fainting or burst blood vessels would be a common occurrence if it wasn’t sufficiently adapted. Many scientists infer, from the fact that giraffes require such powerful hearts, that Brachiosaurus must have had a powerful heart as well, especially considering the physical similarities between the two animals. This theory also makes sense considering a close relative to Brachiosaurus is the bird, which is an animal with an extraordinarily powerful heart for its size.

Physical Attributes

To put it simply, Brachiosaurus was huge. Scientists speculate that an adult may have had the weight equivalent to six or more elephants. With its very long front limbs, shoulder height was almost 24 feet. Its legs were over 13 feet which means they were among the longest in the history of the animal kingdom. Its ribs were deep as well, at 9 feet long and 7 feet wide. Despite its great size, its head was proportionately very small. Even at its small size, there were many holes in the skull to keep it  light for ease of movement. As you can probably imagine, it had a proportionately small brain too.

Predators of Brachiosaurus

Luckily, Brachiosaurus did not need to be very smart to outwit predators. A large size has its advantages and the average adult Brachiosaurus was probably safe from predators who were intimidated by it. The young, old and weak were probably not safe, though. It is estimated that, from the beginning to the end of a Brachiosaurus physical maturation, it ended up increasing its weight 2,000 times so the young Brachiosaurus was much smaller and more vulnerable than the adult. The young and weak were probably preyed upon by aggressive carnivorous dinosaurs like Allosaurus. If Brachiosaurus traveled in packs, which is a likely scenario, the adults could have provided protection to the more vulnerable members of the herd. They also had sharp claws on their feet which could have provided a pretty effective defense against would-be predators just by kicking them.

What Did Brachiosaurus Eat?

Brachiosaurus was a herbivore, which meant it exclusively ate plants and it ate a lot. Scientists estimate that, because of its weight, Brachiosaurus needed to eat over 400 pounds of food every day. The majority of its day was probably spent nipping leaves from treetop branches over 16 feet above ground, and chewing with its spoon-shaped but sharp teeth. It didn’t have teeth capable of grinding its food, so it used small rough stones in its stomach to help it digest food. The late Jurassic period had mostly different plant life than we have today. It was a very warm and humid Tropical environment. The trees it enjoyed were conifers, tree ferns, ginkgoes and cycads.

The Metabolism of a Brachiosaurus

Brachiosaurus was once thought to be emblematic of why dinosaurs couldn’t be endothermic, or controlling body temperature internally, due to its great size and because of the high caloric needs. However, this was found out to be a miscalculation due to lack of knowledge at the time about the large air sacs in the sauropod that would have provided a cooling effect to offset possible overheating from the large size. Scientists had also overestimated its body mass. Now we have a better idea of how the dinosaur gained and lost heat and it lends support to the idea that sauropods were endothermic, including Brachiosaurus.

How Did Brachiosaurus Move?

Many sauropods can rear on its hindlimbs, which could be one reason why Brachiosaurus was depicted in the film Jurassic Park as being capable of rearing on its back legs as well. However, scientists know that it was unsuited for such movement because of its size and the distribution of its weight.

A Fairly Slow Quadraped

Brachiosaurus was quadrapedal, which means it walked on its four legs. It probably wasn’t able to move as fast as many dinosaurs that were smaller, many estimates say 6-10 miles per hour. Fortunately, the Brachiosaurus didn’t need to move fast. When defending the young from predators, the adults probably signaled to them, surrounded them and swiped at attackers with their huge clawed legs.

The Discovery of Brachiosaurus

In 1900, Elmer S. Riggs and his crew, from what is now the Field Museum of Natural History, found the skeleton of Brachiosaurus altithorax among some rocks in the Morrison Formation of Colorado River valley of western Colorado. In 1901, Elmer S. Riggs wrote a report describing the unusual length of the humerus compared to the femur. A photograph was taken showing Riggs’ assistant laying down next to the humerus, which looks to be at least a foot or two longer than the height of the assistant. Riggs also described the huge size overall, plus the strikingly similar way that the overall skeleton compared to a giraffe. He did not name the dinosaur until 1903, calling it Brachiosaurus altithorax and “the largest known dinosaur”. Among sauropods, it is rare and the specimen that Riggs named is the most complete skeleton to this day. Other type species have been found in Africa and Europe and other sauropods, such as Dinodocus and Ultrasaurus- to name a few, have at times been grouped in with Brachiosaurus, but currently none of them are thought to belong in the same genus.

Name that Dinosaur Bone

Brachiosaurus bones had been found before the findings of Riggs and the museum crew, but at the time it was not known to belong to a new animal. A sauropod skull was found in 1883 at Felch Quarry near Garden Park in Colorado and sent to the renowned paleontologist Othniel Charles Marsh, who used the skull in his restoration which he had called Brontosaurus (but was later named Apotosaurus). Then it became part of The National Museum of Natural History and in the 1970s the skull was reevaluated to be called part of Carnarasaurus. In 1998 it was reevaluated again and finally recognized as a Brachiosaurus skull by Kenneth Carpenter and Virginia Tidwell. Discoveries of Brachiosaurus bones in North America have been so rare that we only have a handful of bones attributed to it. Paleontologists have described bones from Colorado, Oklahoma, Wyoming and Utah. Other bones found in the area that were initially thought to be Brachiosaurus were later renamed as other dinosaurs, such as Supersaurus and Ultrasaurus.

The Importance of Brachiosaurus

Brachiosaurus may be a rare dinosaur, but we have enough information about it to have learned a great deal about the species and about dinosaurs in general. The cooling potential of air sacs of Brachiosaurus, for example, provided valuable evidence that an endothermic metabolism is possible in dinosaurs. We also know from the giraffe-like features of Brachiosaurus that, even though the existence of two species may be separated by eons, we can still know a lot about the more distant one by comparing their strikingly similar features.