Diplodocus
Encyclopedia : D : DI : DIP : Diplodocus
Diplodocus (pronounced /ˌdɪ.pləˈdɔ.kəs/ or /dɪˈplɔd.əˌkəs/; meaning "double beam") is a genus of a diplodocid sauropod dinosaur which lived in what is now western North America at the end of the Jurassic Period, about 150 to 147 million years ago. The generic name is in reference to its double-beamed chevron bones (Greek diplos/διπλος meaning 'double' and dokos/δοκος meaning 'wooden beam' or 'bar') was a herbivorous sauropod dinosaur. While not the longest dinosaur known, Diplodocus can boast the longest completely known dinosaur skeleton.
Classification
The genus Diplodocus gives its name to Diplodocidae, the family in which it belongs.Marsh, O.C. 1884. Principal characters of American Jurassic dinosaurs. Part VII. On the Diplodocidae, a new family of the Sauropoda. American Journal of Science 3: 160-168. A subfamily, Diplodocinae, has been created to include Diplodocus and its closest relatives, including Seismosaurus (which may belong to the same genus) and Barosaurus. More distantly related is the contemporaneous Apatosaurus, which is still considered a diplodocid although not a diplodocine.Taylor, M.P. & Naish, D. 2005. The phylogenetic taxonomy of Diplodocoidea (Dinosauria: Sauropoda). PaleoBios 25(2): 1-7. (download [here])Harris, J.D. 2006. The significance of Suuwassea emiliae (Dinosauria: Sauropoda) for flagellicaudatan intrarelationships and evolution. Journal of Systematic Palaeontology 4(2): 185–198. The Portuguese Dinheirosaurus and the African Tornieria have also been identified as close relatives of Diplodocus by some authors.Bonaparte, J.F. & Mateus, O. 1999. A new diplodocid, Dinheirosaurus lourinhanensis gen. et sp. nov., from the Late Jurassic beds of Portugal. Revista del Museo Argentino de Ciencias Naturales. 5(2):13-29. (download [here])Rauhut, O.W.M., Remes, K., Fechner, R., Cladera, G., & Puerta, P. 2005. Discovery of a short-necked sauropod dinosaur from the Late Jurassic period of Patagonia. Nature 435: 670-672.Discovery and species
The first Diplodocus skeleton was found at Como Bluff, Wyoming in 1878 and was named Diplodocus longus ('long double-beam'), by paleontologist Othniel Charles Marsh in 1878Marsh OC. Principal characters of American Jurassic dinosaurs. Part I. American Journal of Science 3; 411-416 (1878)..Marsh later named D. lacustris in 1884, from remains of a smaller animal from Morrison, Colorado. These remains are now believed to have been from an immature animal, rather than from a separate species.
Although not the type species, D. carnegiei (named after Andrew Carnegie) is the best known, mainly due to a near-complete skeleton collected by Jacob Wortman, of the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania and described and named by John Bell Hatcher in 1901.
D. hayi, known from a partial skeleton discovered by William H. Utterback in 1902 near Sheridan, Wyoming, was described in 1924.Holland WJ. The skull of Diplodocus. Memoirs of the Carnegie Museum IX; 379-403 (1924).
Diplodocus remains have been found in the Morrison Formation of the Western US States of Colorado, Utah, Montana and Wyoming. Fossils of this animal are common, except for the skull, which is often missing from otherwise complete skeletons.
Diplodocus species
- D. hallorum (=Seismosaurus hallorum)
- D. lacustris (nomen dubium)
As with the related genus Barosaurus, the very long neck of Diplodocus' is the source of much controversy amongst scientists. A 1992 Columbia University study of Diplodocid neck structure indicated that the longest necks would have required a 1.6 ton heart. The study proposed that animals like these would have had rudimentary auxiliary 'hearts' in their necks, whose only purpose was to pump blood up to the next 'heart' (Lambert).
A presentation [Reappraisal of Seismosaurus, A Late Jurassic Sauropod Dinosaur from New Mexico] at the annual conference of the Geological Society of America, in 2004, made a case for Seismosaurus to be reassigned as a species of Diplodocus, namely D. hallorum.
Paleobiology
Diplodocus was long-necked, with a long, whip-like tail. It was herbivorous. Its teeth were peg-like and positioned only in the anterior part of the jaws. The skull was very small, compared to the huge size of the animal, which could reach up to 27 m (90 feet), although some scientists suggest that the Diplodocus could reach a full length of 45 metres and weigh up to 20 U.S. tons. The braincase is small. The neck is composed of at least fifteen vertebrae.
The fore limbs of Diplodocus were shorter than the hind limbs.
Diplodocus is the longest dinosaur known from a complete skeleton. While dinosaurs such as Seismosaurus (which may be a large Diplodocus anyway) and Supersaurus were probably longer, fossil remains of these animals are fragmentary.
Tail
Diplodocus had an extremely long tail, composed of at around eighty caudal vertebrae
, which is almost double the number some of the earlier sauropods had in their tails; Shunosaurus having 43 and Camarasaurus 53.
The tail may have served as a counterbalance for the neck. The middle part of the tail had 'double beams' (oddly-shaped bones on the underside of the tail), which gave Diplodocus its name. They may have provided support for the vertebrae or perhaps prevented the blood vessels from being crushed if the animal's heavy tail pressed against the ground. These 'double beams' are also seen in some related dinosaurs.
Necks
At first, diplodocids were often portrayed with their necks held high up in the air, allowing them to graze from tall trees. More recently, scientists have argued that the heart would have had trouble sustaining sufficient blood pressure to oxygenate the brain. Furthermore, more recent studies have shown that the structure of the neck vertebrae would not have permitted the neck to bend far upwards. Interestingly, the range of movement of the neck would have allowed the head to graze below the level of the body, leading scientists to speculate on whether Diplodocus grazed on submerged water plants, from riverbanks. This concept of the feeding posture is supported by the relative lengths of front and hind limbs. Furthermore, its peglike teeth may have been used for eating soft water plants.Habitat
Marsh and then HatcherHatcher JB. "Diplodocus (Marsh): Its osteology, taxonomy, and probable habits, with a restoration of the skeleton,". Memoirs of the Carnegie Museum, vol. 1 (1901), pp. 1-63 assumed the animal was aquatic, due to the position of its nasal openings at the apex of the cranium. Later, since the 1970s, general consensus has the sauropods as firmly terrestrial animals. Ironically, with the preceding view of its possible preference for water plants there is a view of a likely riparian habitat for Diplodocus, echoing the original aquatic theory.In popular culture
- Mounted Casts of Diplodocus skeletons are displayed in many museums worldwide, including an unusual D. hayi in the Houston Museum of Natural Science, and D. carnegiei in the Natural History Museum in London, the Natural Science Museum in Madrid, Spain the Field Museum in Chicago and, of course, the Carnegie Museum of Natural History in Pittsburgh. A mounted skeleton of D. longus is at the Smithsonian National Museum of Natural History in Washington, D. C..
- Diplodocus appeared in the second episode of the BBC television series Walking With Dinosaurs.
- In , Doc (presumably for Diplodocus), played by Kris Kristofferson, is a Diplodocus; all the main character long-necks are Apatosaurus.
Footnotes
References
External links
- [Museo Nacional de Ciencias Naturales, Madrid]
- [Diplodocus Marsh, by J.B. Hatcher 1901] Its Osteology, Taxonomy, and Probable Habits, with a Restoration of the Skeleton. Memoirs of the Carnegie Museum, Volume 1, Number 1, 1901. Full text, Free to read.
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