Brachiosaurus

Name Origin

Arm Lizard

Family

Brachiosauridae

Classification

Diapsida, Saurischia, Sauropodomorpha

Habitat (Discovery Location)

United States

Period

Approximately 161 to 146 million years ago (Late Jurassic)

Length

Approximately 25 meters

Weight

Approximately 40 to 70 tons

Diet

Herbivore (Plant-eater)

Description

With a massive figure that could be considered synonymous with the word “dinosaur,” Brachiosaurus has made a name for itself worldwide as the “largest dinosaur in history” since its discovery in 1900.
Although it has now yielded the title of the largest species to dinosaurs like Argentinosaurus, its overwhelming presence remains undiminished today.
True to its name, which means “arm lizard” in Latin, it possesses the unique characteristic of having longer forelimbs than hind limbs.

Size and Characteristics of Brachiosaurus: The Unconventional Physique of the “Arm Lizard”

Brachiosaurus was a super-massive sauropodomorph (herbivorous dinosaur) that lived primarily in North America during the Late Jurassic period.

An Exceptional Style with Long Forelimbs

While typical sauropodomorphs (like Diplodocus) had long hind limbs and a horizontal back, Brachiosaurus was the exact opposite.
Its forelimbs (humeri) connected to the shoulders were developed to be extremely long and thick, while its hind limbs were only about half that size.
It is such an exceptional case among sauropodomorphs that the discoverer initially mistook the forelimb bones for the hind limb bones.
Because of this, its backline sloped backward from the shoulders to the hips like a slide.

Its backline sloped backward from the shoulders to the hips like a slide

Differences from “Giraffatitan”

After the first fossils were discovered by Elmer Riggs in Colorado, USA, in 1900, similar giant fossils were also found in Tanzania, Africa.
Although considered the same species for many years, the African specimens are now distinguished as a separate genus, “Giraffatitan.”
The image of Brachiosaurus that we are so familiar with often heavily reflects the appearance of this Giraffatitan.

The Truth Behind Its Biggest Mystery, the “Neck”: Was Raising It Vertically Impossible?

In encyclopedias and movies, the image of it stretching its neck high vertically like a giraffe to eat tree leaves has been popular.
If raised to the maximum, it would reach a height of 16 meters (about the 5th floor of a building).
However, recent research flatly denies this iconic image.

Reason 1: The Fear of Fainting from Dizziness

Sending blood against gravity to a brain over 10 meters high would require a powerful heart and incredibly high blood pressure.
It is pointed out that if it suddenly raised its neck from a low position, blood would not reach the brain, highly likely causing severe lightheadedness and causing it to faint and collapse.

Reason 2: Skeletal Limits and the “Suspension Bridge” Theory

CT scan investigations revealed that the inside of the neck bones (cervical vertebrae) were sparse cavities, with the thinnest parts being less than the thickness of a postcard.
It would be impossible to attach massive muscles to support the neck vertically.
Currently, the leading idea is the “suspension bridge theory,” where the hind limbs and pelvis act as main towers, suspending everything from the neck to the tail with strong ligaments.

The “suspension bridge theory” suspending from neck to tail with strong ligaments

The “Horizontal Posture Theory” Derived from 3D Simulations

In 2005, a 3D analysis by Michael Parrish and others revealed that the range of motion for moving the neck up and down was at most about 20 degrees from the horizontal.
On the other hand, because the side-to-side range of motion was wide, the current mainstream view is the “horizontal posture theory,” which suggests they ate by sweeping across a wide range of plants while keeping their massive bodies still and their necks at an angle close to parallel to the ground.
Furthermore, the action of “standing up on only its hind legs,” as depicted in the movie “Jurassic Park,” was physically impossible because its hind legs were too short.

Why Did They Evolve Such Long Necks?

If it wasn’t for eating leaves from tall trees, why did they make their necks extremely long, even bearing disadvantages like the risk of fainting and restricted movement?

The hint lies in the fossils of their young (juveniles).
A child’s neck was not as long as an adult’s.
Features that develop significantly as an animal reaches adulthood are biologically considered to be “sexual appeal (display) for reproduction.”
In other words, a prominent theory is that they evolved their necks as a sign of strength and maturity, prioritizing the reproductive advantage of “the longer the neck, the more attractive to the opposite sex” over practical life benefits.

The Phantom Aquatic Lifestyle Theory and the Life of a Giant Glutton

Complete Refutation of the Aquatic Lifestyle Theory

It was once thought that “to alleviate their heavy body weight with buoyancy, they lived in the water of swamps and lakes, exposing only the nostrils on the top of their heads.”
However, it has been discovered that if their massive bodies submerged in water, water pressure would crush their lungs, making breathing impossible. Furthermore, it was found that their nostrils were located at the front (snout) rather than on top of the head. Today, it is confirmed that they lived entirely on land.

A Diet of Eating for 20 Hours a Day

Brachiosaurus was a purely herbivorous dinosaur.
In a very small skull—only about 50 cm relative to its body—grew teeth shaped like pencils or spatulas.

How They Ate

Without chewing, they used their thick mouths to bite off conifers and ferns, swallowing them whole in large quantities.

Digestion

They swallowed “gastroliths” (stomach stones) to help grind up the food and aid digestion.

Eating Time

To obtain energy from low-nutrition plants, they spent about 20 hours a day eating.

It is thought that they had an extremely high energy efficiency due to a mechanism called “gigantothermy,” where their massive bodies experienced little temperature fluctuation (or they were warm-blooded animals with a high metabolic rate).

Moving in Large Herds and Defense

Based on dense clusters of fossilized footprints, it is believed they possessed the sociality to travel in large herds of hundreds.

Brachiosaurus moving in a herd

They maintained a rational cycle of migrating to areas abundant in food.
Also, when predators like Allosaurus appeared, it seems they used their massive bodies as shields and swung their long tails like whips as weapons.

The Jurassic Giant Holding Evolutionary Mysteries

Although fossils of Brachiosaurus are rarely found outside Late Jurassic strata, their lineage was passed down for a long time, as related species have been confirmed even in the Early Cretaceous.
The debates surrounding their unique proportions with long forelimbs and the angle of their necks continue to fascinate many people today.
With new discoveries in the future, the image of this great “arm lizard” will surely be updated into something even more astonishing.

Jurassic
Park / World Featured Dinosaur

Role in the Film (Spoiler Alert!)

Appearance in Jurassic Park
This is one of the dinosaurs that left a powerful and lasting impression on audiences in Jurassic Park.

This Brachiosaurus was the very first dinosaur that Dr. Alan Grant's group encountered in the flesh upon arriving on the island. The scene where it rears up on its hind legs right in front of them, calmly feeding on leaves high overhead, gave the audience an overwhelming sense of scale and realism, filling them with a profound sense of awe.

It has two main appearances in the film: this initial encounter, and the scene where it appears near the tree that Dr. Grant and the children climbed while escaping the Tyrannosaurus.
Appearance in Jurassic Park III
The individuals featured in this film are the population inhabiting Isla Sorna.

Compared to the Isla Nublar individuals seen in the first and fifth films, their appearance is significantly different; they have a greenish body color and, most notably, a red coloration on their heads. This difference in color is officially established as sexual dimorphism. The most prominent individuals in the film are the males, with official stats listing them at 15.8 meters long and 15.5 meters tall.

Their main role in the movie occurs during the film's climax, in the scene where the group is despondent after believing they have lost Billy (or so they think). The majestic appearance of the Brachiosaurus before them is portrayed as a symbol of hope for the group in their desperate situation.
Appearance in Jurassic World: Fallen Kingdom
The Brachiosaurus population appearing in this film is believed to consist of individuals transported from Isla Sorna, in addition to those that survived the collapse of the original Jurassic Park.

During the operational period of the fourth film, Jurassic World, Brachiosaurus was neither raised nor exhibited to the public. Therefore, it is believed that both the new arrivals and the individuals that had established their own ecosystem since the first film were living together on the island in a feral state.

Midway through the story, a Brachiosaurus is seen calmly wandering the deserted ruins of the park's Main Street. In a way, its unchanged majestic form served to welcome Owen and his team upon their return to Isla Nublar.

As many dinosaurs perished in the volcanic eruption, one lone survivor barely managed to flee to the dock at the edge of the island.

In fact, this individual was the very same "first Brachiosaurus" that appeared before Dr. Alan Grant's group in the first film, famously rearing up on its hind legs to feed.

However, its colossal size proved to be its undoing, making it impossible to load onto the rescue transport ship. As the people on the departing vessel watched in tears, unable to jump into the ocean, the Brachiosaurus was left behind. It was consumed by the approaching pyroclastic flow and smoke, letting out a heartbreaking cry as it perished—one of the most tragic and memorable deaths in the entire series.

Regarding this striking scene with the pyroclastic flow, it seems that using a different dinosaur was initially considered during the production stage.

However, the director stated that ending the island's story with the first dinosaur ever encountered on Isla Nublar was the "right choice." This decision carried deep narrative significance: by depicting the death of the Brachiosaurus, which symbolized the "beginning" of the series, the film portrayed the complete and final collapse of the "site of dreams" that was Isla Nublar.

While the individual at the dock could not be saved, the species Brachiosaurus itself narrowly managed to avoid facing re-extinction.

According to the "Arcadia's manifest" seen in the film, it is confirmed that another adult was captured and safely transported to the mainland. Additionally, since its name can be seen in the embryo storage case at the end of the story, it is implied that DNA samples were also successfully secured.
Appearance in Jurassic World: Dominion
The tragic death of the individual left behind on Isla Nublar in the previous film, Jurassic World: Fallen Kingdom, remains a heartbreaking memory for many viewers.

However, the Brachiosaurus lineage did not end there. In this film, it appears that several other individuals were successfully captured; they are shown living safely within the protected confines of the "Biosyn Sanctuary."

Furthermore, according to information from the official promotional website "Dinotracker," their presence has been confirmed not only within the sanctuary but also in various locations around the world.

Specific sightings have been reported in Finland, Brazil, and across the wider South American region, indicating that they are expanding their range to encompass environments from freezing cold climates to the tropics.

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Brachiosaurus

Description