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Apatosaurus

2007 Schools Wikipedia Selection. Related subjects: Dinosaurs

   iApatosaurus

                         Fossil range: Late Jurassic

                 Conservation status

   Extinct (fossil)
              Scientific classification

   Kingdom:    Animalia
   Phylum:     Chordata
   Class:      Sauropsida
   Superorder: Dinosauria
   Order:      Saurischia
   Suborder:   Sauropodomorpha
   Infraorder: Sauropoda
   Family:     Diplodocidae
   Genus:      Apatosaurus
               Marsh, 1877

                                   Species

     * A. ajax
     * A. excelsus
     * A. louisae

                       Synonyms

     * Brontosaurus Marsh, 1879c
     * Elosaurus Peterson & Gilmore, 1902

   Apatosaurus ( IPA: [/əˈpæ.təˌsɔː.rəs/]), previously known as
   Brontosaurus, is a genus of sauropod dinosaurs that lived about 140
   million years ago, during the Jurassic Period. They were some of the
   largest land animals that ever existed, about 4.5 metres (15 feet) tall
   at the hips, with a length of up to 21m (70 feet) and a mass up to 35
   metric tonnes (40 tons). Their name means 'deceptive lizard', so-named
   because the chevron bones were like those of Mosasaurus ( Greek
   apatelos or apatelios meaning 'deceptive' and sauros meaning 'lizard').

   The cervical vertebrae and the bones in the legs were bigger and
   heavier than that of Diplodocus although, like Diplodocus, Apatosaurus
   also had both a long neck and a long tail. The tail was held above the
   ground during normal locomotion. Like most sauropods, Apatosaurus had
   only a single large claw on each forelimb. The skull was first
   identified in 1975, a century after this dinosaur acquired its name.

Discovery and species

   Fossils of this animal have been found in Nine Mile Quarry and Bone
   Cabin Quarry in Wyoming and at sites in Colorado, Oklahoma and Utah,
   USA.
     * A. ajax is the type species of the genus, and was named by the
       paleontologist Othniel Charles Marsh in 1877 after Ajax, the hero
       from Greek mythology. It is the holotype for the genus and two
       partial skeletons have been found, including part of a skull.
     * A. excelsus (originally Brontosaurus) was named by Marsh in 1879.
       It is known from six partial skeletons, including part of a skull,
       which have been found in the United States, in Oklahoma, Utah, and
       Wyoming.
     * A. louisae was named by William Holland, in 1915. It is known from
       one partial skeleton, which was found in Colorado, in the United
       States.

   Robert T. Bakker made A. yahnahpin the type species of a new genus,
   Eobrontosaurus in 1998, so it is now properly Eobrontosaurus yahnahpin.
   It was named by Filla, James and Redman in 1994. One partial skeleton
   has been found in Wyoming.

   On March 23, 1983 the Apatosaurus was made the official state dinosaur
   of Guam.

Paleobiology

   Early on, it was believed that Apatosaurus was too massive to support
   its own weight on dry land, so it was theorized that the sauropod must
   have lived partly submerged in water, perhaps in a swamp. Recent
   findings do not support this. In fact, like its relative Diplodocus,
   Apatosaurus was a grazing animal with a very long neck and a long tail
   that served as a counterweight. Fossilized footprints indicate that it
   probably lived in herds. To aid in processing food, Apatosaurus may
   have swallowed gizzard stones ( gastroliths) in the same way that many
   birds do today, as its jaws lacked molars with which to chew tough
   plant fibers.

Neck

   Apatosaurus browsed the tops of trees, on riverbanks. Scientists
   believe that these sauropods could not raise their necks to an angle of
   90 degrees, as doing so would slow blood flow to the brain excessively;
   blood starting at the body proper would take two or more minutes to
   reach the brain. Furthermore, studies of the structure of the neck
   vertebrae have revealed that the neck was not as flexible as previously
   thought.

Physiology

   With such a large body mass, combined with a long neck, physiologists
   encounter problems determining how these animals managed to breathe.

   Beginning with the assumption that Apatosaurus, like crocodilians, did
   not have a diaphragm, the dead-space volume (the amount of unused air
   remaining in the mouth, trachea and air tubes after each breath) has
   been estimated at about 184 liters for a 30kg specimen.

   Its tidal volume (the amount of air moved in or out during a single
   breath) has been calculated based on the following respiratory systems:
     * 904 liters if avian
     * 225 liters if mammalian
     * 19 liters if reptilian

   On this basis, its respiratory system could not have been reptilian, as
   its tidal volume would not have been able to replace its dead-space
   volume. Likewise, the mammalian system would only provide a fraction of
   new air on each breath. Therefore, it must have had either a system
   unknown in the modern world or one like birds, i.e. multiple air sacs
   and a flow-through lung.

   Furthermore, an avian system would only need a lung volume of about 600
   liters compared to a mammalian requirement of 2,950 liters, which would
   exceed the available space. The overall thoracic volume of Apatosaurus
   has been estimated at 1,700 liters allowing for a 500-liter,
   four-chambered heart (like birds, not three-chambered like reptiles)
   and a 900-liter lung capacity. That would allow about 300 liters for
   the necessary tissue.

   Assuming Apatosaurus had an avian respiratory system and a reptilian
   resting-metabolism (it certainly could not fly), it would need to
   consume only about 262 liters (69 gallons) of water per day.

   It is not known how Apatosaurs ate enough food to satisfy their
   enormous bodies. It is likely that they ate constantly, pausing only to
   cool off, drink or to remove parasites. It is surmised that they slept
   standing upright. They likely relied on their enormous size and herd
   behaviour to deter predators.

Lips

   According to Robert Bakker, it is a major possibility that Apatosaurus
   may have had thick, moose-like lips.

Classification

   Apatosaurus is a member of the Diplodocidae, along with Diplodocus,
   Barosaurus and Seismosaurus, although it is not as closely related to
   the others as they are to each other and hence placed in its own
   subfamily Apatosaurinae.

Apatosaurus/Brontosaurus controversy

   Apatosaurus' correct head
   Enlarge
   Apatosaurus' correct head

   In 1877, Othniel Charles Marsh published notes on his discovery of
   Apatosaurus ajax. He followed this in 1879 with a description of
   another, more complete, dinosaur specimen. He speculated that the
   latter specimen represented a new genus and named it Brontosaurus
   excelsus. In 1903, it was discovered that Brontosaurus excelsus was in
   fact an adult Apatosaurus and the name Apatosaurus, having been
   published first, was deemed to have priority as the official name;
   Brontosaurus was relegated to being a synonym. In the 1970s, it was
   proven that the traditional "Brontosaurus" image known to all was, in
   fact, an Apatosaurus excelsus with a Camarasaurus head incorrectly
   placed on its body.

In popular culture

Film and television

     * Apatosaurus are featured in the Walking with Dinosaurs special "The
       Ballad Of Big Al" and in When Dinosaurs Roamed America.
     * Littlefoot from the 1987 film, The Land Before Time was an
       Apatosaurus.
     * The Flintstones made frequent reference to "Brontosaurus burgers"
       and steaks.

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   with only minor checks and changes (see www.wikipedia.org for details
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