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a herbivorous brachiosaurid sauropod dinosaur from the Late Jurassic of North America.
Pronunciation: BRAK-ee-oh-SOR-us
Meaning: Arm lizard
Author/s: Riggs (1903)
Synonyms: None known
First Discovery: Colorado, U.S.A.
Chart Position: 63

Brachiosaurus altithorax

Upon discovery in 1900, Elmer Samuel Riggs hailed Brachiosaurus altithorax as "the largest known dinosaur" and at the time he was dead right. Since then though, much larger dinosaur remains have been discovered, and heck, it may not even be the biggest member of its own family—Brachiosauridae. Problem is, brachiosaurids are pretty rare, their remains—some big, some huge—are mostly fragmentary, and each critter may have been different proportionately. On top of that, there is some dispute about which animals belong to this family and until more, and more complete, remains turn up it's all "ifs", "buts" and "maybes".

The forelimbs of Brachiosaurus were much longer than its hind limbs, but they were all surprisingly slender, and its chest was remarkably deep. These giraffe-like proportions meant its long, thick-set neck was more vertically oriented than other sauropods, so it required a shorter counter-balancing tail. But its raised neck also raised questions about blood flow and how it managed to get oxygen to its tiny head which has, itself, courted plenty of speculation down the years.

Once upon a long ago paleontologists surmised that Brachiosaurus was a sea-dweller and its stout, dome-topped noggin with nostrils on top acted as a kind of pre-historic snorkel. This theory has since been blown out of the water as its lungs couldn't work under the pressure of total submersion, its nostrils were probably closer to the end of its snout, and its feet were too narrow to use as flippers. Funnily enough, the shorter, dome-profiled skull mentioned above actually belongs to Giraffatitan from Tendaguru—the critter once known as Brachiosaurus brancai. But that critter was officially severed from Brachiosaurus in 2009 by Mike Taylor, who found the two beasties differed in shape and proportion of almost every comparable body part.

Although huge, the neck and trunk of Brachiosaurus (and other saurischian dinosaurs, such as Aerosteon and Sauroposeidon) contained air sacs which were connected fore and aft to the lung, and created "air holes" by invading the vertebrae and ribs—a process known as pneumatization. This invasion would significantly reduce the overall bone density of what would appear to be a massive, lumbering oaf. But the air sacks may also have bellowed air through a rigid lung thus creating a one-way "flow-through" system, which means that breathed in the same way as a much smaller and more familiar critter... the modern bird!

Unlike other sauropods who were probably able to double or perhaps treble their reach by rearing up on their hind legs, this front-loaded dinosaur with a forward-positioned center of mass was ill-equipped to do so. Fortunately, long front legs and a deep chest meant its neck left its body at a much steeper angle than other sauropods, so while its powerful jaws and chisel-like teeth were ideally suited to dealing with tough, lower-lying foliage it could conceivably browse from treetops, where the most tender leaves reside.
(Arm lizard) Etymology
Brachiosaurus is derived from the Greek "brachion" (arm) and "sauros" (lizard) referring to its unusually long humerus (upper arm).
The species epithet, altithorax, is derived from the Latin altus meaning "deep" and thorax meaning "breastplate" because of its unusually deep and wide chest cavity.
The first Brachiosaurus fossils were discovered at Riggs Quarry 13, in the Brushy Basin Member of the Morrison Formation, Grand River Canyon, western Colorado, U.S.A by H. W. Menke on July 4, 1900. A skull which was discovered at Felch Quarry 1, Garden Park, Colorado in 1983, and used to reconstruct Marsh's "Brontosaurus" (now Apatosaurus) may belong to a species of Brachiosaurus.
The holotype (FMNH P 25107) is a partial skeleton including the last seven back (dorsal) vertebrae, sacrum, first two neck (caudal) vertebrae, left shoulder bone, material from the right "arm" and leg, and some ribs.
Era: Mesozoic
Epoch: Late Jurassic
Stage: Kimmeridgian-Tithonian
Age range: 156-151 mya
Est. max. length: 26 meters
Est. max. hip height: 5 meters
Est. max. weight: 30 tons
Diet: Herbivore
Other Species?
Brachiosaurus brancai was discovered in the famous Tendaguru beds of Tanzania and named by Werner Janensch in 1914. It was tagged Brachiosaurus "Giraffatitan" brancai by Greg Paul in 1988 and officially moved to its own genus—Giraffatitan—by Mike Taylor in 2009.
Brachiosaurus fraasi (Janensch, 1914) was later synonymized with Brachiosaurus brancai but now belongs to Giraffatitan.
Brachiosaurus alataiensis (de Lapparent and Zbyszewski, 1957) from Portugal is now known as Lusotitan.
Brachiosaurus nougaredi (de Lapparent, 1960) was found disjointed and strewn around eastern Algeria's Sahara Desert, and there lies the problem. Its remains include a forelimb that was found several hundred metres east of a sacrum, a tibia that was found 800 m west of the sacrum, and some metatarsals that were found somewhere in between. De Lapparent hints that the arm and tibia were too fragile to extract. But its 1300mm long four-vertebrae sacrum, which was probably 5-verts long when complete, is longer than the corresponding lump of bone in all known sauropods barring Apatosaurus louisae (1325 mm) and Argentinosaurus (1350 mm) even in its partial state, and the latter pair are 5 verts long and complete! "Brachiosaurus nougaredi" may be one of the largest sauropods ever found. It may also be several different species rolled into one, and none of them seem particularly Brachiosaurus-like. Brachiosaurus nougaredi may be responsible for the huge fossilised footprints in Morocco that are known as Breviparopus.
• Riggs ES (1903) "Brachiosaurus altithorax, the largest known dinosaur".
American Journal of Science (series 4)
• Upchurch P, PM Barrett and P Dodson (2004) Chapter Thirteen: "Sauropoda" in Weishampel, Osmólska and Dodson "The Dinosauria: Second Edition".
• Taylor MP (2009) "A re-evaluation of Brachiosaurus altithorax Riggs 1903 (Dinosauria, Sauropoda) and its generic separation from Giraffatitan brancai (Janensh 1914)".
Journal of Vertebrate Paleontology 29(3):787–806.
• Wedel MJ (2003) "Vertebral pneumaticity, air sacs, and the physiology of sauropod dinosaurs".
Paleobiology, 29(2), 2003, pp. 243–255.
• Antunes M and O Mateus (2003) "Dinosaurs of Portugal".
• Mallison H (2011) "Rearing Giants – kinetic-dynamic modeling of sauropod bipedal and tripodal poses" in Klein, Remes, Gee & Sander "Biology of the Sauropod Dinosaurs: Understanding the Life of Giants".
• de Lapparent AF (1960) "Les dinosauriens du "continental intercalaire" du Sahara central" ("The dinosaurs of the 'continental intercalaire' of the central Sahara").
Memoires of the Geological Society of France, Volume. XXXIX, Issues 1-6.
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To cite this page:
Atkinson, L. "BRACHIOSAURUS :: from DinoChecker's dinosaur archive".
›. Web access: 18th Feb 2018.