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Ankylosaurus

2007 Schools Wikipedia Selection. Related subjects: Dinosaurs

   iAnkylosaurus

                        Fossil range: Late Cretaceous

               Scientific classification

   Kingdom:    Animalia
   Phylum:     Chordata
   Class:      Sauropsida
   Superorder: Dinosauria
   Order:      Ornithischia
   Suborder:   Thyreophora
   Infraorder: Ankylosauria
   Family:     Ankylosauridae
   Genus:      Ankylosaurus
   Species:    A. magniventris

                                Binomial name

   Ankylosaurus magniventris
   Brown, 1908

   Ankylosaurus ( pronounced /æŋˈkɪloʊˌsɔɹəs/ or /æŋˈkaɪloʊˌsɔɹəs/,
   meaning 'stiffened lizard') is a genus of ankylosaurid dinosaur,
   containing one species, A. magniventris. Fossils of Ankylosaurus are
   found in geologic formations dating to the very end of the Cretaceous
   Period in western North America.

   Although a complete skeleton has not been discovered and several other
   species are represented by more extensive fossil material, Ankylosaurus
   is often considered the archetypal armored dinosaur. Other
   ankylosaurids shared its well-known features, like the heavily-armored
   body and massive bony tail club, but Ankylosaurus was the largest
   member of its family, approximately the size of a large rhinoceros.

Paleobiology

   A full-grown Ankylosaurus was a very large animal, compared to the
   majority of modern land animals. Some scientists have estimated a
   length of 9 meters (30 ft.). Another reconstruction suggests a
   significantly smaller size, at 6.25 m (20.5 ft) long, up to 1.5 m
   (5 ft) wide and about 1.7 m (67 in) high at the hip. The body shape was
   low-slung and very wide. Ankylosaurus was quadrupedal, with the
   hindlimbs longer than the forelimbs. Although its feet are still
   unknown to science, comparisons with other ankylosaurs suggest
   Ankylosaurus probably had five toes on each foot. The skull was low and
   triangular in shape, wider than it was long. The largest known skull
   measures 64.5 centimeters (25 in) long and 74.5 cm (29 in) wide. Like
   other ankylosaurs, Ankylosaurus was herbivorous, with very small,
   leaf-shaped teeth suitable for cropping vegetation. Ankylosaurus did
   not share the grinding tooth batteries of the contemporaneous
   ceratopsid and hadrosaurid dinosaurs, indicating that very little
   chewing occurred. Bones in the skull and other parts of the body were
   fused to increase their strength.

Armor

   The most obvious feature of Ankylosaurus is its armor, consisting of
   massive knobs and plates of bone, known as osteoderms, embedded in the
   skin. Osteoderms are also found in the skin of crocodiles, armadillos
   and some lizards. The bone was probably overlain by a tough, horny
   layer of keratin. These osteoderms ranged greatly in size, from wide,
   flat plates to small, round nodules. The plates were aligned in regular
   horizontal rows down the animal's neck, back, and hips, with the many
   smaller nodules protecting the areas between the large plates. Smaller
   plates may have been arranged on the limbs and tail. Compared to the
   slightly more ancient ankylosaurid Euoplocephalus, the plates of
   Ankylosaurus were very smooth in texture, without the high keels found
   on the armor of the contemporaneous nodosaurid Edmontonia. A row of
   flat, triangular spikes may have protruded laterally along each side of
   the tail. Tough, rounded scales protected the top of the skull, while
   four large pyramidal horns projected outwards from its rear corners.

Tail club

   The famous tail club of Ankylosaurus was also composed of several large
   osteoderms, which were fused to the last few tail vertebrae. It was
   very heavy and supported by the last seven tail vertebrae, which
   interlocked to form a stiff rod at the base of the club. Thick tendons
   have been preserved, which attached to these vertebrae. These tendons
   were partially ossified (or bony) and were not very elastic, allowing
   great force to be transmitted to the end of the tail when it was swung.
   It seems to have been an active defensive weapon, capable of producing
   enough of a devastating impact to break the bones of an assailant. It
   has also been proposed that the tail club acted as a decoy for the
   head, although this idea is now largely discredited.

Environment

   Ankylosaurus magniventris existed between 68 to 65 million years ago,
   in the latest Maastrichtian stage of the Late Cretaceous Period, and
   was one of the last dinosaurs to exist just prior to the
   Cretaceous-Tertiary extinction event. The type specimen is from the
   Hell Creek Formation of Montana, while other specimens have been found
   in the Lance Formation of Wyoming and the Scollard Formation in
   Alberta, Canada, all of which date to the very end of the Cretaceous.

   The Lance, Hell Creek and Scollard Formations represent different
   sections of the western shore of the shallow sea that divided western
   and eastern North America during the Cretaceous. They represent a broad
   coastal plain, extending eastwards from the seaway to the newly-formed
   Rocky Mountains. These formations are composed largely of sandstone and
   mudstone, which have been attributed to floodplain environments. The
   Hell Creek is the best studied of these ancient environments. At the
   time, this region was subtropical, with a warm and humid climate. Many
   plant species were supported, primarily angiosperms, with less common
   conifers, ferns and cycads. An abundance of fossil leaves found at
   dozens of different sites indicates that the area was largely forested
   by small trees.

   Fossils of Ankylosaurus are very rare in these sediments, compared to
   Edmontosaurus and the super-abundant Triceratops, which make up most of
   the large herbivore fauna. Another ankylosaur, Edmontonia, is also
   found in the same formations. However, Ankylosaurus and Edmontonia seem
   to have been separated both geographically and ecologically.
   Ankylosaurus had a wide muzzle, perhaps used for non-selective grazing
   and may have been limited to the upland regions, away from the coast,
   while Edmontonia had a narrower muzzle, indicating a more selective
   diet and seems to have lived at lower elevations, closer to the coast.

Classification

   Ankylosaurus was named as the type genus of the family Ankylosauridae.
   Ankylosaurids are members of the larger taxon Ankylosauria, which also
   contains the nodosaurids. Ankylosaur phylogeny is a contentious topic,
   with several mutually exclusive analyses presented in recent years, so
   the exact position of Ankylosaurus within Ankylosauridae is unknown.
   Ankylosaurus and Euoplocephalus are often thought to be sister taxa.
   However, other analyses have found these genera in different positions.
   Further discoveries or research may clarify the situation.

Discovery

   Ankylosaurus was named by American paleontologist Barnum Brown, in
   1908. The generic name is derived from the Greek words αγκυλος/ankulos
   ('curved') and σαυρος/sauros ('lizard'). Brown intended this name in
   the same sense as the medical term ankylosis, to refer to the stiffness
   produced by the fusion of many bones in the skull and body, so the name
   is often translated as 'stiffened lizard.' The type species is A.
   magniventris, from the Latin magnus ('great') and venter ('belly'),
   referring to the great width of the animal's body.

   A team led by Brown discovered the type specimen of A. magniventris
   (AMNH 5895) in the Hell Creek Formation of Montana, in 1906. This
   consisted of the top of the skull, as well as vertebrae, ribs, part of
   the shoulder girdle and armor. Six years earlier, Brown found the
   skeleton of a large theropod dinosaur (AMNH 5866) in the Lance
   Formation of Wyoming. This specimen was named Dynamosaurus imperiosus
   in 1905 but is now thought to belong to Tyrannosaurus rex. Associated
   with AMNH 5866 were more than 75 osteoderms of various sizes, which
   were attributed to Dynamosaurus. However, these osteoderms are nearly
   identical in form to those of A. magniventris and most probably belong
   to this species. In 1910, while on an expedition to Alberta, Barnum
   Brown recovered his third specimen of A. magniventris (AMNH 5214), from
   the Scollard Formation. AMNH 5214 includes a complete skull and the
   first known tail club, as well as ribs, limb bones and armor. All three
   of the above specimens are now housed at the American Museum of Natural
   History in New York City. The largest known skull of this animal (NMC
   8880) was collected in Alberta by Charles M. Sternberg, in 1947 and is
   now housed at the Canadian Museum of Nature. Many other isolated bones,
   armor plates and teeth have been found over the years.

In popular culture

   Since its description in 1908, Ankylosaurus has been publicized as the
   archetypal armored dinosaur, and due to its easily recognizable
   appearance and the intense public interest in dinosaurs, Ankylosaurus
   has been a feature of worldwide popular culture for many years. A
   life-sized reconstruction of Ankylosaurus featured at the 1964 World's
   Fair in New York City greatly contributed to its popularity.

   Several motion picture series have featured ankylosaurs. Starting with
   Godzilla Raids Again in 1955, several films in the Japanese Godzilla
   series featured Anguirus, a gigantic creature similar in both name and
   appearance to Ankylosaurus. Anguirus begins as an enemy but later
   becomes a loyal ally to Godzilla. Ankylosaurus also has brief cameos in
   the Land Before Time series throughout the late 1980s and 1990s, though
   never a large part. Ankylosaurus is one of several types of dinosaur
   shown grazing together in the 2001 film Jurassic Park III. Ankylosaurus
   has also been featured on the television documentary miniseries Walking
   With Dinosaurs (1999) and The Truth About Killer Dinosaurs (2005), both
   produced by the BBC.
   Retrieved from " http://en.wikipedia.org/wiki/Ankylosaurus"
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