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Spinosaurus

2007 Schools Wikipedia Selection. Related subjects: Dinosaurs

   iSpinosaurus

                        Fossil range: mid Cretaceous

              Scientific classification

   Kingdom:     Animalia
   Phylum:      Chordata
   Class:       Sauropsida
   Superorder:  Dinosauria
   Order:       Saurischia
   Suborder:    Theropoda
   Superfamily: Megalosauroidea
   Family:      Spinosauridae
   Genus:       Spinosaurus
                Stromer, 1915

                                   Species

     * S. aegyptiacus ( type)
     * ?S. marocannus

   Spinosaurus (meaning 'spine lizard') was a theropod dinosaur genus that
   lived in what is now Egypt, from the Albian to early Cenomanian stages
   of the Cretaceous Period, about 95 to 93 million years ago. According
   to a study by dal Sasso et al. (2006), it was the largest of all
   carnivorous dinosaurs by a significant margin, even larger than
   Tyrannosaurus rex and Giganotosaurus. Spinosaurus was the longest
   theropod, measuring 15 to 17.4 metres (49.2 to 57.1 feet) long and
   standing at 5 to 6 metres (16 to 20 feet) in height. Spinosaurus
   reached weights up to 9 tons.

   The distinctive spines of these animals (large bones extending from the
   vertebrae) grew up to 2 m (6.6ft) long and were likely to have had skin
   stretching between them, forming a sail-like structure, although some
   have suggested they were covered in muscle and formed a hump or ridge.

   Spinosaurus provides the name of a family of dinosaurs, the
   Spinosauridae, of which other members include Angaturama (probably
   synonymous with Irritator), Baryonyx, Irritator, Suchomimus, and
   Siamosaurus.

Description

   Although Spinosaurus is well-known to dinosaur enthusiasts due to its
   unusual features, it is mostly known from remains that have been
   destroyed, aside from a few more recently discovered teeth and skull
   elements. Jaw and skull material published in 2006 show that it had one
   of the longest skulls of any carnivorous dinosaur, estimated by dal
   Sasso et al. at about 175 cm (5.7 ft).

   Originally found in the Bahariya Valley of Egypt in 1912, it was named
   by German paleontologist Ernst Stromer in 1915. Some of the fossils
   were damaged during transport back to the Deutsches Museum, Munich,
   Germany and the remaining bones were completely lost due to Allied
   bombing in 1944.

   Aside from its 'sail', notable characteristics of Spinosaurus include:
     * A long, narrow snout, similar to other Spinosaurids and, like them,
       filled with conical teeth.
     * One enlarged, hook-like claw on each of its front limbs, perhaps
       for catching fish.
     * Relatively short legs and long 'arms', leading some paleontologists
       to suggest it may have been quadrupedal, rather than strictly
       bipedal (though it was undoubtedly capable of at least facultative
       bipedality).

   Much of this is speculation based on Baryonyx and other spinosaurids,
   as no limb material has ever been attributed to Spinosaurus itself.

   Since its discovery, Spinosaurus has held the record for longest, and
   possibly largest, theropod dinosaur (though this fact did not reach the
   public consciousness until its depiction in the film Jurassic Park III
   and the description of a new specimen in 2006). Both Huene (1926) and
   Glut (1982) listed it as the most massive theropod in their surveys, at
   upwards of 6 tons in weight and 15 meters (50 feet) in length. Paul
   (1988) also listed it as the longest theropod at 15 meters (50 feet),
   but gave a lower mass estimate. The most recent estimates, based on new
   specimens described by dal Sasso et al. (2006), list Spinosaurus at 16
   - 18 metres (53.3 to 60 feet) long and 7.5 - 9 tons in weight. At least
   one survey, as-yet unpublished, suggest that Spinosaurus reached sizes
   of 12 - 19 tons in weight. These high-end weight estimates are based on
   the fact that the vertebrae of Spinosaurus are unusually massive
   compared to theropods of comparable size (implying an extremely large
   overall mass), and that the holotype specimens are apparently
   sub-adult.

Diet

   It is unclear whether Spinosaurus was primarily a cursorial predator or
   a fisher, as indicated by its elongated jaws, conical teeth and raised
   nostrils. The only direct evidence for spinosaur diet comes from
   related European and South American species. Baryonyx was found with
   both fish scales and bones from juvenile Iguanodon in its stomach,
   while a tooth embedded in a South American pterosaur bone suggests that
   spinosaurs occasionally preyed on these flying archosaurs. Spinosaurus
   was likely to have been a more generalized and opportunistic predator,
   possibly a Cretaceous equivalent of large grizzly bears, being biased
   toward fishing, though it undoubtedly scavenged and took many kinds of
   small-to-medium-sized prey (Paul, 1988).

Sail

   Spinosaurus sails were unusual, although other dinosaurs of the same
   time and area, namely the ornithopod Ouranosaurus and the sauropod
   Rebbachisaurus, developed a similar structural adaptation of their
   dorsal vertebrae. The sail is possibly analogous (not homologous) to
   that of the Permian mammal-like reptile, Dimetrodon, which lived before
   the dinosaurs even appeared (these similarities are presumably due to
   parallel evolution).

   The purpose of these sails is uncertain; scientists have proposed
   several hypotheses:
     * Heat regulator. If the sail contained abundant blood vessels, the
       animal could have used the sail's large surface area to absorb
       heat. This would imply that the animal was only partly warm-blooded
       at best and lived in climates where nighttime temperatures were
       cool or low and the sky usually not cloudy. It is thought that
       Spinosaurus and Ouranosaurus both lived in or at the margins of an
       earlier version of the Sahara Desert, which could explain this. It
       is also possible that the sail was used to radiate excess heat from
       the body, rather than to collect it. Large animals, due to the
       relatively small ratio of surface area of their body compared to
       the overall volume (Haldane's principle), face far greater problems
       of dissipating excess heat at higher temperatures than gaining it
       at lower. Sails of these dinosaurs added considerably to the skin
       area of the body, with minimum increase of volume. Furthermore, if
       the sail was turned away from the sun, or positioned at a 90 degree
       angle towards a cooling wind, the animal would quite effectivly
       cool itself in the warm climate of Cretaceous Africa.
     * Sexual display. Elaborate body structures of many modern-day
       animals usually serve to attract members of opposite sex during
       mating. It is quite possible that the sails of these dinosaurus
       were used for courtship, in a way similar to a peacock's tail. If
       this was the case, the sails may have been brightly colored, but
       this is purely speculative.
     * Intimidating device. The sail was possibly used to intimidate
       rivals or frighten enemies, making the animal appear to be bigger
       than it was. The dinosaur could display its sail as a final warning
       signal, before it would resort to open attack, like modern-day
       rattlesnakes use their tail.

   Finally, since things in nature rarely develop for a singular reason,
   it is quite possible that the sail combined all these functions, acting
   normally as a heat regulator, becoming a courting aid during the mating
   season, being used to cool itself and, on occasions, turning into an
   intimidating device when an animal was feeling threathened. Conjecture
   may even allow that the sail may have changed colour, during any of
   these functions.

Species and Specimens

   Two species of Spinosaurus have been named: Spinosaurus aegyptiacus
   ("Egyptian spine lizard") and Spinosaurus marocannus ("Moroccan spine
   lizard"). S. marocannus was originally described by Russell as a new
   species based on the length of its neck vertebrae. However, several
   later authors considered the length of the neck vertebrae to be
   variable from individual to individual and therefore consider S.
   marocannus to be a synonym of S. aegyptiacus .

   Five partial specimens of Spinosaurus have been found, the first having
   been destroyed during World War II (luckily, detailed drawings and
   descriptions of the specimen remain). The probable size of these
   individual spinosaurs can be estimated using comparison to known
   material from other spinosaurid dinosaurs.
     * IPHG 1912 VIII 19 (Stromer, 1915) (destroyed during allied bombing
       in WWII)
          + Size: 17.4 m, 12-19 tons (subadult)
          + Material: (skull ~1.45 m) maxillary fragment, incomplete
            dentary (mandible ~1.34 m), nineteen teeth (62, 126 mm), two
            incomplete cervical vertebrae, seven dorsal vertebrae (190-210
            mm), dorsal ribs, gastralia, eight caudal centra.
     * CMN 50791 (Russell, 1996)
          + Material: mid cervical vertebra (195 mm), anterior dorsal
            neural arch, anterior dentary, mid dentary.
          + Note: holotype of Spinosaurus marocannus.
     * MNHN SAM 124 (Taquet and Russell, 1998)
          + Size: ~17 m, ~11-18 tons (adult)
          + Material: (skull ~1.42 m) partial premaxillae, partial
            maxillae, vomers, dentary fragment.
     * Office National des Mines nBM231 (Buffetaut and Ouaja, 2002)
          + Material: anterior dentary.
     * MSNM V4047 (Dal Sasso et al., 2006)
          + Size: ~21 m, ~20-32 tons
          + Material: (skull ~1.75 m) premaxillae, partial maxillae,
            partial nasals

   Rauhut (2003) suggested that Stromer's Spinosaurus holotype was a
   chimera, consisting of dorsal vertebrae from a carcharodontosaurid
   similar to Acrocanthosaurus and a dentary from a large theropod similar
   to Baryonyx. This analysis, however, was rejected by dal Sasso and most
   other researchers.

Spinosaurus in Jurassic Park III

   Spinosaurus achieved widespread fame as the main antagonist in Jurassic
   Park III. It is portrayed as larger, more powerful and more vicious
   than Tyrannosaurus, epitomized by a scene in which the two resurrected
   predators battle and Spinosaurus emerges victorious by snapping the
   rex's neck, establishing itself in the movie as the new main predator.

   No such battle could ever have taken place in real life, since
   Spinosaurus and Tyrannosaurus lived thousands of miles and millions of
   years apart.

   Spinosaurus did, however, share its habitat with two other theropods
   that equalled or exceeded T. rex in size: the massive carnosaur
   Carcharodontosaurus and the large but relatively lightweight abelisaur
   Deltadromeus. Although the three gigantic predators probably occupied
   different ecological niches, they may have occasionally come into
   conflict over prey or territory.
   Retrieved from " http://en.wikipedia.org/wiki/Spinosaurus"
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   with only minor checks and changes (see www.wikipedia.org for details
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