Brachiosaurus altithorax was described by Elmer
Riggs in 1903 based on a specimen from the
Late Jurassic (156 to 145 million years ago) of Colorado.
However, the best skeletons are from the
Tendaguru Hills of Tanzania, which, at the time
the skeletons were collected, was known as German
East Africa. Field work started in 1909 and
continued until 1912. The dig was not a small affair.
Almost $600,000 was raised to fund the dig. In
1909, 170 workers were employed, and their numbers
swelled to 500 in 1911 and 1912. About 235
metric tons of fossil material was removed. No
permits for further fieldwork have been issued for
this area since the 1920's.
Characteristics
Brachiosaurus was a quadrupedal, herbivorous dinosaur
whose forelimbs were longer than its hind
limbs. This sauropod had a very long neck which
it held erect and a short tail which was held out
horizontally. Spoon-shaped teeth filled most of
the jaws. The nostrils were positioned on a large,
dome-shaped crown over the eyes. The enlarged
nasal cavity may have been used to produce
sounds. If not, the animal must have had a keen
sense of smell. Brachiosaurus was between 22.5
and 25 meters (85 feet) long, 16 meters (52 feet)
high, and weighed between fifty and eighty tons.
The animals had a maximum speed of between
twenty to thirty kilometers per hour. Unlike
Apatosaurus, Brachiosaurus is a relatively rare
sauropod in the western United States, hinting
that it may have lived a solitary existence there
rather than being part of a herd.
With its long, erect neck and long forelimbs,
Brachiosaurus could feed on the cones and leaves
of the tallest trees (conifers, cycads, and gingkoes).
By feeding in the treetops, Brachiosaurus
did not compete with other sauropods, such as
Apatosaurus, or stegosaurs, such as Kentrosaurus,
which fed at lower levels. To supply the brain with
blood, Brachiosaurus's heart would have to pump
at a systolic pressure of more than 630, have had
four chambers, and weighed about 400 kilograms
(about 882 pounds). In comparison, humans' normal
systolic pressure is somewhere between 120
and 130, with a heart that weighs about 300 grams
(10.5 ounces). To help move the blood along, the
artery wallsmayhave been heavily muscularized,
and a reservoir of oxygenated blood may have existed
in the head for emergencies, when the animal
was forced to change the level of its head rapidly.
Classification:
Kingdom: Animalia
Subkingdom: Bilateria
Phylum: Chordata
Subphylum: Vertebrata
Class: Reptilia
Subclass: Dinosauria
Order: Saurischia (lizard-hipped dinosaurs)
Suborder: Sauropoda (long-necked herbivores)
Family: Brachiosauridae (quadrupedal herbivores whose
forelimbs were longer than their hind limbs)
Genus and species: Brachiosaurua altithorax, B. atalaiensis, B.
brancai, and B. nougaredi
Note: A number of competing classification schemes exist
and will probably continue to do so in the future.
Geographical location: Late Jurassic of Algeria (B.
nougaredi), Colorado and Utah (B. altithorax), Portugal
(B. atalaiensis), and Tanzania (B. brancai)
Habitat: In the United States, Brachiosaurus is a relatively
rare sauropod in the dry habitats represented by the
Morrison Formation; in Tanzania, Brachiosaurus was far
more numerous in the mesic (moist) habitats characteristic
of the Tendaguru Formation
Gestational period: Although no eggs have been found,
Brachiosaurus was undoubtedly an egg layer; the frequency
at which eggs were laid, the time it took for the
eggs to hatch, and the reproductive life span of the
adults are unknown
Life span: Based on mammalian models, sexual maturity
would be reached after ten years and the life span was
probably in excess of one hundred years
Special anatomy: The neural spines on the cervical vertebrae
of the brachiosaurids were not V-shaped as they
were in the diplodocids; instead, the neural spines on the
vertebrae at the junction of the neck and back were
highly elongate for attachment of the muscles that
held the neck and head erect, resulting in a pronounced
hump over the shoulders; the centrum of
each vertebra contained several pleurocoels
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