Brachiosaurus is a scientifically confirmed genus of sauropod dinosaur. This colossal herbivore, recognizable by its extremely long neck and unique body structure, is one of the largest land animals known from the fossil record. It existed during the Mesozoic Era, leaving behind physical evidence that confirms its existence.
Brachiosaurus: Defining Classification and Time Period
Brachiosaurus is classified within the Sauropoda, a group of large, quadrupedal, plant-eating dinosaurs characterized by long necks and tails. It belongs to the family Brachiosauridae, a lineage distinguished by its unique body proportions. The scientific name, Brachiosaurus altithorax, was established based on the type species found in North America.
This dinosaur roamed the Earth during the Late Jurassic period, specifically the Kimmeridgian to Tithonian ages (approximately 155.6 to 145.5 million years ago). It shared its North American habitat with other famous sauropods, such as Apatosaurus and Diplodocus. Brachiosaurus appears to have been a less common find in the fossil record.
The Story of Discovery and Naming
The physical evidence for Brachiosaurus was first uncovered in 1900 in the Morrison Formation of western Colorado, near the Colorado River valley. American paleontologist Elmer S. Riggs, working for the Field Columbian Museum, led the expedition that recovered the partial postcranial skeleton. Riggs initially believed the bones belonged to an already-known sauropod but soon recognized the specimen’s unique proportions.
Riggs formally named and described the new dinosaur in 1903, assigning it the name Brachiosaurus altithorax. The genus name Brachiosaurus translates from Greek to “arm lizard,” referencing the unusual length of its forelimbs. The species name altithorax means “deep chest,” describing the considerable depth of the animal’s trunk cavity.
Many popular museum mounts are based on an African specimen once considered a species of Brachiosaurus. However, modern analysis determined that these African fossils represented a distinct genus, now called Giraffatitan. The American specimen, B. altithorax, remains the definitive type specimen for the genuine Brachiosaurus genus.
Anatomy and Lifestyle: The High Browser
The distinguishing anatomical feature of Brachiosaurus is its body configuration, which differs from most other sauropods. Its forelimbs were notably longer than its hind limbs, resulting in a steeply inclined trunk that sloped upward toward the shoulders. This gave the dinosaur a giraffe-like posture.
This unique anatomy dictated a specialized lifestyle as a high browser, allowing it to feed on foliage well above the ground. With its neck extended, the head of an adult Brachiosaurus could reach an estimated 9 to 13 meters (30 to 43 feet) above the ground. This height gave it access to the leaves and branches of tall trees, such as conifers, ginkgos, and tree ferns.
Length estimates range from 18 to 22 meters (59 to 72 feet). Based on the type specimen, weight estimates typically fall between 28 and 47 metric tons. Its massive size and specialized feeding height made it a dominant consumer of the high-canopy vegetation in its Late Jurassic environment.