Brachiosaurus

Brachiosaurus //, meaning "Arm Lizard", from the Greek brachion/βραχιων meaning 'arm' and sauros/σαυρος meaning 'lizard', was a genus of sauropod dinosaur which lived during the Late Jurassic period.

It was thus named because its forelimbs were longer than its hind limbs. One of the largest animals ever to walk the earth, it has become one of the most famous of all dinosaurs and is widely recognized worldwide.

For many decades, Brachiosaurus was the largest dinosaur known. It has since been discovered that a number of giant titanosaurids (the Argentinosaurus, for example) surpassed Brachiosaurus in terms of sheer mass. More recently, another brachiosaurid, Sauroposeidon, has also been discovered; based on incomplete fossil evidence. It too is likely to have outweighed Brachiosaurus.

Brachiosaurus is often considered to be the largest dinosaur known from a relatively complete fossilized skeleton. However, the largest known specimens, including the Brachiosaurus in the Humboldt Museum of Berlin (excavated in Africa, the tallest mounted skeleton in the world), are now considered by some scientists to be part of the Giraffatitan genus.

Brachiosaurus is estimated to have weighed between 30 to 80 tonnes (35 to 90 tons). It is believed to have reached 13 meters (42 feet) in height, and 25 meters (82 feet) in length. Estimates higher than these numbers are usually based on the Ultrasauros, which was originally considered to be an extremely large Brachiosaurus. However, Ultrasauros is now believed to be an erroneously-reconstructed chimera, composed of neck bones from Supersaurus and a shoulder bone (scapulacoracoid) from the smaller Brachiosaurus.

Discovery and species

The first Brachiosaurus was discovered in 1900 by Elmer S. Riggs, in the Grand River Canyon of western Colorado, in the United States.

Brachiosaurus species

Brachiosaurus includes three known species:

B. alataiensis de Lapparent & Zbyszewski, 1957: Is known from back bones (vertebrae), and parts of the hip and limbs, which were recovered in Estremadura, Portugal. It lived about 150 million years ago, during the Kimmeridgian age of the Late Jurassic period.
B. altithorax Riggs, 1903: The type species is known from two partial skeletons recovered in Colorado and Utah in the United States. It lived from 145 to 150 million years ago, during the Kimmeridgian to Tithonian ages.
?B. nougaredi de Lapparent, 1960: While it may not be a distinct species (nomen dubium?) it is known from set of fused bones over the hip (sacrum) and parts of a forelimb, which were recovered in Wargla, Algeria in Africa. It lived 100 to 110 million years ago, during the Albian to Cenomanian ages of the middle Cretaceous period.

The best specimens of Brachiosaurus were from the species B. brancai, which was found in the Tendaguru Beds of Tanzania, in Africa in 1909 by Werner Janensch. In 1991, George Olshevsky placed them in a new genus, Giraffatitan, because they do not share derived characteristics with Brachiosaurus. Giraffatitan has withers over its shoulder, and a rounded crest over its nostrils.

Giraffatitan brancai Janensch, 1914 (formerly B. brancai): The new type species, it is known from five partial skeletons, including at least three skulls and some limb bones, which were recovered in Mtwara, Tanzania, in Africa. It lived from 145 to 150 million years ago, during the Kimmeridgian to Tithonian ages of the Late Jurassic period.

Description and environment

Brachiosaurus was a sauropod, one of a group of four-legged, plant-eating dinosaurs with long necks and tails and relatively small brains. Unlike other families of sauropods, it had a giraffe-like build, with long forelimbs and a very long neck. Brachiosaurus had spatulate teeth (resembling chisels), well-suited to its herbivorous diet. Its skull featured a number of holes, probably aiding weight-reduction. The first toe on its front foot and the first three toes on its hind feet were clawed.

Skull

While Brachiosaurus has traditionally been characterized by its distinctive, high-crested skull, many scientists now assign the specimen, upon which this depiction was based, to the genus Giraffatitan. However, one complete Brachiosaurus skull is known. This skull, which had been the skull Marsh used on his early reconstructions of Brontosaurus, was studied by Carpenter and Tidwell in 1998 and found actually to belong to one of the North American Brachiosaurus species. The skull of Brachiosaurus is more camarasaur-like than the distinctive high-crested skull of Giraffatitan and it lends support to the existence of Giraffatitan as a distinct genus.

Metabolism

Like other "long-necked" dinosaurs, Brachiosaurus may not have been able to pump sufficient oxygenated blood from its heart to its brain if it raised its head high above its shoulders, though this is disputed by some researchers.

If the Brachiosaurus was endothermic (warm-blooded), it would have taken an estimated ten years to reach full size. If it were instead poikilothermic (cold-blooded), then it would have required over 100 years to reach an equivalent peak mass. As a warm-blooded animal, the daily energy demands of Brachiosaurus would have been enormous; it would probably have needed to consume more than 400 lb. (~200 kg) of food per day. If Brachiosaurus was fully cold-blooded or was a passive bulk endotherm, it would have needed far less food to meet its daily energy needs.

Environment and behavior

Brachiosaurus was one of the largest dinosaurs of the Jurassic era; it lived on prairies filled with ferns, bennettites, horsetails and it moved through vast conifer forests, groves of cycads, Seed ferns, and Ginkgos. Some of its contemporary species included Stegosaurus, Dryosaurus, Apatosaurus, and Diplodocus. While it is speculated that groups of Brachiosaurus moved in herds, fully-grown individuals had little to fear from even the largest predators of the time, Allosaurus and Torvosaurus, on account of their sheer size.

Brachiosaurus nostrils, like the huge corresponding nasal openings in its skull, were long thought to be located on the top of the head. In past decades, scientists theorized that the animal used its nostrils like a snorkel, spending most of its time submerged in water in order to support its great mass. The current consensus view, however, is that Brachiosaurus was a fully terrestrial animal. Studies have demonstrated that water pressure would have prevented the animal from breathing effectively while submerged and that its feet were too narrow for efficient aquatic use. Furthermore, new studies by Larry Witmer (2001) show that, while the nasal openings in the skull were placed high above the eyes, the actual nostrils would still have been close to the tip of the snout (a study which also lends support to the idea that the tall "crests" of brachiosaurs supported some sort of fleshy resonating chamber).

Berlin's G. brancai and Chicago's high flyer

A Brachiosaurus skeleton is mounted in the B Concourse of United Airlines' Terminal One in O'Hare International Airport in Chicago, courtesy of the Field Museum of Chicago. It is a model, not a collection of fossils.

A famous specimen of Giraffatitan brancai mounted in Berlin, sometimes considered a species or sub-genus of Brachiosaurus, is one of the largest mounted skeletons in the world.

Beginning in 1909, Werner Janensch found many additional brachiosaur specimens in Tanzania, Africa, including some nearly complete skeletons, which were widely used in Brachiosaurus reconstructions. These are now considered to be Giraffatitan fossils.

In popular culture

Brachiosaurus appeared in two of the three Jurassic Park movies. In the first movie they are seen when the scientists land on the island. Later, the herd interacts with some people in a tree. In Jurassic Park III, another herd is seen on Isla Sorna, first from the view of an airplane and later from a boat.

Brachiosaurus also made an appearance in the Walt Disney movie Dinosaur. Only one was shown, an older female who was the last of her kind.

Brachiosaurus appeared briefly in the second episode of Walking with Dinosaurs to show the great achievements of sauropods.

References

External links

Expect awe-struck travelers, from the Field Museum. (O'Hare airport mount)

Jurassic Park species | Brachiosaurs | North American dinosaurs | Jurassic dinosaurs | Cretaceous dinosaurs

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