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Diplodocus

2007 Schools Wikipedia Selection. Related subjects: Dinosaurs

   iDiplodocus

                         Fossil range: Late Jurassic

   Diplodocus skull
   Diplodocus skull

                             Conservation status

   Extinct (fossil)
              Scientific classification

   Kingdom:    Animalia
   Phylum:     Chordata
   Class:      Sauropsida
   Superorder: Dinosauria
   Order:      Saurischia
   Suborder:   Sauropodomorpha
   Infraorder: Sauropoda
   Family:     Diplodocidae
   Genus:      Diplodocus
               Marsh, 1878

                                   Species

   See text.

   Diplodocus ( pronounced /ˌdɪ.pləˈdɔ.kəs/ or /dɪˈplɔd.əkəs/; meaning
   "double beam") is a genus of diplodocid sauropod dinosaur which lived
   in what is now western North America at the end of the Jurassic Period.
   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'). The chevrons, initially believed to be unique to
   Diplodocus, have since then been discovered in other diplodocids.

   Diplodocus, a herbivorous sauropod dinosaur, was one of the more common
   dinosaurs found in the Upper Morrison Formation, about 150 to 147
   million years ago, in an environment and time dominated by giant
   sauropods , such as Camarasaurus, Barosaurus, Apatosaurus and
   Brachiosaurus . It is among the most easily identifiable dinosaurs,
   with its classic dinosaur shape, long neck and tail and four sturdy
   legs. For many years it was the longest dinosaur known. Its great size
   may have been a deterrent to predators such as Allosaurus and
   Ceratosaurus.

Description

   One of the best known sauropods, Diplodocus was a very large
   long-necked quadrupedal animal, with a long, whip-like tail. Its
   forelimbs were slightly shorter than its hind limbs, resulting in a
   largely horizontal posture. The long-necked, long-tailed animal with
   four sturdy legs has been mechanically compared with a suspension
   bridge. In fact, Diplodocus is the longest dinosaur known from a
   complete skeleton. While dinosaurs such as Seismosaurus (which might be
   a large Diplodocus) and Supersaurus were probably longer, fossil
   remains of these animals are only fragmentary.

   The skull of Diplodocus was very small, compared to the size of the
   animal, which could reach up to 27  metres (90 feet), of which 6 metres
   was neck. Diplodocus had small, 'peg'-like teeth only at the anterior
   part of the jaws, which were distinctly procumbent . Its braincase was
   small. The neck was composed of at least fifteen vertebrae and is now
   believed to have been generally held parallel to the ground and unable
   to have been elevated much past horizontal .
   Diplodocus tail, Natural History Museum, London.
   Enlarge
   Diplodocus tail, Natural History Museum, London.
   Diplodocus - Bone formation in the tail.
   Enlarge
   Diplodocus - Bone formation in the 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 (such as Shunosaurus with 43), and far
   more than conteporaneous macronarians had (such as Camarasaurus with
   53). There has been speculation as to whether it may have had a
   defensive or noisemaking function.

   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.

Discovery and species

   Several species of Diplodocus were described between 1878 and 1924. The
   first skeleton was found at Como Bluff, Wyoming by Benjamin Mudge and
   Samuel Wendell Williston in 1878 and was named Diplodocus longus ("long
   double-beam"), by palaeontologist Othniel Charles Marsh in 1878.
   Diplodocus remains have since been found in the Morrison Formation of
   the western U.S. 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. Although not the type species, D.
   carnegiei is the most completely known and most famous due to the large
   number of casts of its skeleton in museums around the world.

   The two Morrison Formation sauropod genera Diplodocus and Barosaurus
   had very similar limb-bones. In the past, many isolated limb bones were
   automatically attributed to Diplodocus but may, in fact, have belonged
   to Barosaurus.

Valid species

     * D. longus, the type species, is known from two skulls and a caudal
       series from the Morrison Formation of Colorado and Utah.
     * 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.
     * D. hallorum better known as Seismosaurus hallorum. A presentation
       at the annual conference of the Geological Society of America, in
       2004, made a case for Seismosaurus, discovered in 1979 and
       recognised as a separate genus in 1991, to be reassigned as a
       species of Diplodocus, namely D. hallorum.

Nomina dubia (Dubious species)

     * D. lacustris is a nomen dubium, named by Marsh 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.

Palaeobiology

   Current posture with horizontal neck, NHM, London.
   Enlarge
   Current posture with horizontal neck, NHM, London.

   Due to a wealth of skeletal remains, Diplodocus is one of the best
   studied dinosaurs. Many aspects of its lifestyle have been subject to
   various theories over the years. Marsh and then Hatcher assumed the
   animal was aquatic, due to the position of its nasal openings at the
   apex of the cranium. A classic 1910 reconstruction by Dr. Oliver P. Hay
   depicts two Diplodocus with splayed lizard-like limbs on the banks of a
   river. Dr. Hay made an argument in favour for Diplodocus having a
   sprawling, lizard-like gait with widely-splayed legs, and was supported
   by Dr. Gustav Tornier. However, this hypothesis was put to rest by Dr.
   W. J. Holland, who demonstrated that a sprawling Diplodocus would have
   needed a trench to pull its belly through.

   The idea of an aquatic existence was later debunked, as the water
   pressure on the chest wall of Diplodocus was proven to have been too
   great for the animal to have breathed. Since the 1970s, general
   consensus has the sauropods as firmly terrestrial animals, browsing on
   trees. Later still, interestingly, 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.

Neck

   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.

   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).

Spines

   Recent discoveries have suggested that Diplodocus and other diplodocids
   may have had narrow, pointed keratinous spines lining their back, much
   like those on an iguana. This radically different look has been
   incorporated into recent reconstructions, notably Walking with
   Dinosaurs. It is unknown exactly how many diplodocids had this trait.

Trunk

   There has been speculation over whether the high nasal openings in the
   skull meant that Diplodocus may have had a trunk. A recent study
   surmised there was no paleoneuroanatomical evidence for a trunk. It
   noted that the facial nerve in an animal with a trunk, such as an
   elephant, is large as it innervates the trunk. The evidence is that it
   is very small in Diplodocus. Studies by Lawrence Witmer (2001)
   indicated that, while the nasal openings were high on the head, the
   actual, fleshy nostrils were situated much lower down on the snout. .

Growth rate

   Following a number of bone histology studies, Diplodocus, along with
   other sauropods, grew at a very fast rate, reaching sexual maturity
   just over a decade, though continuing to grow throughout their lives.
   Previous thinking held that sauropods would keep growing slowly
   throughout their lifetime, taking decades to reach maturity.

Diet

   Diplodocus had highly unusual teeth compared to other sauropods. The
   crowns were long and slender, elliptical in cross-section, while the
   apex forms a blunt triangular point. The most prominent wear facet is
   on the apex, though unlike all other wear patterns observed within
   sauropods, Diplodocus wear patterns are on the labial (cheek) side of
   both the upper and lower teeth. What this means is Diplodocus and other
   diplodocids had a radically different feeding mechanism than other
   sauropods. Unilateral branch-stripping is the most likely feeding
   behaviour of Diplodocus , as it explains the unusual wear patterns of
   the teeth (coming from tooth-food contact). In unilateral
   branch-stripping one tooth row would have been used to strip foliage
   from the stem, whilst the other would act as a guide and stabiliser.

   With a laterally and dorsoventrally flexible neck, and the possibilty
   of using its tail and rearing up on its hind limbs (tripodal ability),
   Diplodocus would have had the ability to browse at many levels (low,
   medium, and high), up to approximately 12 metres from the ground.

Classification

   Diplodocus is both the type genus of, and gives its name to
   Diplodocidae, the family in which it belongs. Members of this family,
   while still massive, are of a markedly more slender build compared with
   other sauropods such as the titanosaurs and brachiosaurs. All are
   characterised by long necks and tails and a horizontal posture, with
   forelimbs shorter than hindlimbs. Diplodocids flourished in the Late
   Jurassic of North America and possibly Africa and appear to have been
   replaced ecologically by titanosaurs during the Cretaceous.

   A subfamily, Diplodocinae, was erected 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, as it is a member of the subfamily Apatosaurine. The
   Portuguese Dinheirosaurus and the African Tornieria have also been
   identified as close relatives of Diplodocus by some authors.

In popular culture

   A statue of Diplodocus carnegiei in Pittsburgh, Pennsylvania.
   Enlarge
   A statue of Diplodocus carnegiei in Pittsburgh, Pennsylvania.

   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 Senckenberg
   Museum in Frankfurt, Germany, the Field Museum of Natural History 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 was featured in the second episode of the award-winning BBC
   television series Walking With Dinosaurs. The episode "Time of the
   Titans" follows the life of a simulated Diplodocus 152 million years
   ago.

   In the animated film The Land Before Time VI: The Secret of Saurus
   Rock, the character "Doc" (presumably short for Diplodocus), voiced by
   Kris Kristofferson, was a Diplodocus; in contrast to the "long-neck"
   protagonists, which were Apatosaurus.

   Diplodocus had cameo appearances in The Land That Time Forgot and in
   The Lost World (2001).
   Retrieved from " http://en.wikipedia.org/wiki/Diplodocus"
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   with only minor checks and changes (see www.wikipedia.org for details
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