Brachiosaurus
Name: Brachiosaurus
(Arm lizard).
Phonetic: Brak-he-o-dore-us.
Named By: Elmer S. Riggs - 1903.
Classification: Chordata, Reptilia, Dinosauria,
Saurischia, Sauropoda, Titanosauriformes, Brachiosauridae.
Species: B. altithorax (type).
Type: Herbivore.
Size: Up to 26 meters long.
Known locations: USA, Morrison formation.
Time period: Kimmeridgian of the Jurassic.
Fossil representation: Several specimens, the most
complete of which is believed to have come from a sub adult.
The
sauropod
dinosaur Brachiosaurus
earned its name from the fact that the arms, or rather the fore legs
as it was
quadrupedal, are actually longer than the hind legs. The fact that
these are longer offers Brachiosaurus a passive
advantage in reaching up
into the tree canopy to feed as the neck is always arched upwards as a
result. Since the skeleton and vertebrae would be angled in such a
way, Brachiosaurus would not need extra powerful
muscles to lift the
head and neck all the way up, reducing the effort to feed in such a
specialised way. A
further adaptation were the presence of air sacs located along the
neck and trunk of Brachiosaurus. These connected
to the lungs and had
the effect of lowering the body density which in turn would reduce the
total weight of the neck and trunk areas.
These
adaptations meant that Brachiosaurus could
easily live the life
of a high browser feeding upon the tree canopy. Such specialisation
also meant that Brachiosaurus would not have to
compete with other
herbivorous dinosaurs such as the low browsing Stegosaurus.
Brachiosaurus could not chew its food as its jaws
were only capable of
opening and closing. Because of this it would use its spatulate
(chisel like) teeth to crop the vegetation from the tops of trees.
Its
possible that Brachiosaurus was gigantothermic
meaning its massive
body would hold onto body heat for longer than a smaller animal. This
would give Brachiosaurus a higher metabolism than
a 'standard' cold
blooded or 'ectothermic' animal. However, the air sacs that
would have been present inside of the body may also have provided extra
cooling allowing Brachiosaurus to lower its body
temperature and
metabolism. This would also reduce the required calorie intake to
keep its body going, reducing the required amount of time for feeding.
Fossils
that were very similar to Brachiosaurus
were recovered from the
Tendaguru formation in Africa in 1914. This new species was given
the name Brachiosaurus branchai, but upon further
study of the
bones, several morphological differences were discovered, and while
the new specimen was similar to B. altithorax,
it was still
different enough to be considered separate. B. brancai
has since
been renamed Giraffatitan,
with the type species changed to G.
brancai.
It
was once thought that Brachiosaurus had a skull
like Giraffatitian,
but when that was split off into its own group a possible key
difference came to light. The crest forming bone that rises from the
top of the skull of Giraffatitian, is much
smaller in Brachiosaurus
fossils. This crest was once thought to contain the nostrils but
modern reconstruction places the nostrils further along the snout.
This has led to speculation that this may have instead been a form of
resonating chamber that could have been used to amplify the calls of
Brachiosaurus.
Further reading
- Brachiosaurus altithorax, the largest known
dinosaur. - American
Journal of Science, series 4 15:299-306. - Elmer S. Riggs - 1903.
- Structure and relationships of opisthocoelian dinosaurs. Part II. The
Brachiosauridae. - Geological Series (Field Columbian Museum) 2 (6):
229–247. - E. S. Riggs - 1904.
- Die Sch�del der Sauropoden Brachiosaurus, Barosaurus
und
Dicraeosaurus aus den Tendaguru-Schichten
Deutsch-Ostafrikas. -
Palaeontographica (Suppl. 7) 2: 147-298. - W. Janensch - 1935/6.
- New brachiosaur material from the Late Jurassic of Utah and Colorado.
- The Great Basin Naturalist 47 (4): 592–608. - J. A. Jenson - 1987.
- The brachiosaur giants of the Morrison and Tendaguru with a
description of a new subgenus, Giraffatitan, and a
comparison of the
world's largest dinosaurs. - Hunteria 2 (3). - G. S. Paul - 1988.
- Preliminary description of a Brachiosaurus skull
from Felch Quarry 1,
Garden Park, Colorado, by K. Carpenter & V. Tidwell. In The
Upper Jurassic Morrison Formation: An Interdisciplinary Study. Modern
Geology, 23:1-4, K. Carpenter, D. Chure & J. Kirkland (eds.).
- Biostratigraphy of dinosaurs in the Upper Jurassic Morrison Formation
of the Western Interior, USA, by C. E. Turner & F. Peterson. In
Vertebrate Paleontology in Utah. Miscellaneous Publication 99-1. Salt
Lake City, Utah: Utah Geological Survey. pp. 77–114. (David G. Gillete
(ed.)). - 1999.
- Paleoecological analysis of the vertebrate fauna of the Morrison
Formation (Upper Jurassic), Rocky Mountain region, U.S.A. - New Mexico
Museum of Natural History and Science Bulletin, 23. Albuquerque, New
Mexico: New Mexico Museum of Natural History and Science. - J. R.
Foster - 2003.
- First occurrence of Brachiosaurus (Dinosauria,
Sauropoda) from the
Upper Jurassic Morrison Formation of Oklahoma. - PaleoBios 24 (2):
12–21. - M. F. Bonnan & M. J. Wedel - 2004.
- Brachiosaurus altithorax. - Jurassic West: The Dinosaurs of the
Morrison Formation and Their World. Indiana University Press. pp.
205–208. - J. Foster - 2007.
- In vitro digestibility of fern and gymnosperm foliage: implications
for sauropod feeding ecology and diet selection. - Proceedings of the
Royal Society B 275: 1015–1021. - J. Hummel, C. T. Gee, K.-H. S�dekum,
P. M. Sander, G. Nogge & M. Clauss - 2008.
- 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. -
M. P. Taylor - 2009.
- Correction: A re-evaluation of Brachiosaurus altithorax
Riggs 1903
(Dinosauria, Sauropoda) and its generic separation from Giraffatitan
brancai (Janensch 1914). - Journal of Vertebrate Paleontology
31 (3):
727. - M. P. Taylor - 2011.
-
Redescription of Brachiosaurid Sauropod Dinosaur Material From the
Upper Jurassic Morrison Formation, Colorado, USA. - Anatomical Record.
303 (4): 732–758. - Michael D D'Emic & Matthew T Carrano - 2020.
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