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Titanosaur

2007 Schools Wikipedia Selection. Related subjects: Dinosaurs

   iTitanosaurs

                      Fossil range: Jurassic-Cretaceous

                Scientific classification

   Kingdom:     Animalia
   Phylum:      Chordata
   Class:       Sauropsida
   Superorder:  Dinosauria
   Order:       Saurischia
   Suborder:    Sauropodomorpha
   Infraorder:  Sauropoda
   (unranked)   Titanosauria
                Bonaparte & Coria, 1993
   Superfamily: Titanosauroidea
                Lydekker, 1895
   Family:      Titanosauridae
                Lydekker, 1895

                                   Genera

   See text.

   Titanosaurs were a diverse group of sauropod dinosaurs, which included
   Saltasaurus and Isisaurus. This family includes some of the heaviest
   creatures ever to walk the earth, such as Argentinosaurus and
   Paralititan — which might have weighed up to 100 tonnes (110 short
   tons) or, perhaps, even double that, if some poorly-described data is
   believed (see Bruhathkayosaurus). They were named after the
   mythological ' Titans', the early deities of Ancient Greece, who
   preceded the Twelve Olympians.

Characteristics

   Titanosaurs had small heads, even when compared to other sauropods. The
   head was also wide, similar to the heads of Camarasaurus and
   Brachiosaurus but more elongated. Their nostrils were large
   ('macronaria]]n') and they all had crests formed by these nasal bones.
   Their teeth were either somewhat spatulate (spoon-like) or like pegs or
   pencils, but were always very small.

   Their necks were relatively short, for sauropods, and their tails were
   whip-like, but not as long as a diplodocid. While the pelvis (hip area)
   was slimmer than some sauropods, the pectoral (chest area) was much
   wider, giving them a uniquely 'wide-gauged' stance. As a result, the
   fossilised trackways of titanosaurs are distinctly broader than other
   sauropods. Their forelimbs were also stocky but their rear limbs were
   longer. Their vertebrae (back bones) were solid (not hollowed-out),
   which may be a throwback to more primitive saurischians. Their spinal
   column was more flexible, so they were probably more agile than their
   cousins and better at rearing up.

   From skin impressions found with the fossils, it has been determined
   that their skin was armored with a small mosaic of small, bead-like
   scales around a larger scale. One species has even been discovered with
   bony plates, like the Ankylosaurus.

   While they were all huge, many were fairly average in size compared to
   the other giant dinosaurs. There were even some island-dwelling dwarf
   species, probably the result of allopatric speciation and insular
   dwarfism.

Browsing and grazing diet

   Fossilized dung associated with late Cretaceous titanosaurids has
   revealed phytoliths, silicified plant fragments, that offer clues to a
   broad, unselective plant diet. Besides the plant remains that might
   have been expected, such as cycads and conifers, discoveries published
   in 2005 revealed an unexpectedly wide range of monocotyledons,
   including palms and grasses ( Poaceae), including ancestors of rice and
   bamboo, which has given rise to speculation that herbivorous dinosaurs
   and grasses co-evolved.

Nesting grounds

   A large titanosaurid nesting ground was recently discovered in Auca
   Mahuevot, in Patagonia, Argentina and another colony has reportedly
   been discovered in Spain. The small eggs, about 11–12 cm (4–5 in.) in
   diameter, contained fossilised embryos, complete with skin impressions
   (though there was no indication of feathers or dermal spines).
   Apparently several hundred female saltasaurs dug holes, laid their eggs
   and then buried them under dirt and vegetation. This gives evidence of
   herd behavior, which, along with their armor, may have been a defensive
   behaviour against large predators like the Abelisaurus.

Range

   The titanosaurs were the last great group of sauropods before the
   Cretaceous-Tertiary extinction event, about 65–90 million years ago and
   were the dominant herbivores of their time. The fossil evidence
   suggests they replaced the other sauropods, like the diplodocids and
   the brachiosaurids, which died out between the late Jurassic and the
   mid-Cretaceous Periods.

   They were widespread, especially in the southern continents (then part
   of the supercontinent of Gondwana) and even in Australia, where
   sauropod remains in Queensland have recently been determined to be
   titanosaurid. Only Antarctica appears never to have been populated by
   titanosaurs.

Classification

   For such a widespread and successful group (they represent roughly a
   third of the total sauropod diversity known to date), the fossil record
   of titanosaurs is poor. Only recently have skulls or relatively
   complete skeletons (see Rapetosaurus) of any of the roughly 50 species
   of titanosaur been discovered. Many are poorly known and much of the
   material may either be deemed invalid or be reclassified as
   understanding of the clade grows. The anchor taxon, Titanosaurus, is
   particularly poorly known and no longer considered a valid taxon.

   The family Titanosauridae was named after the poorly known and probably
   invalid genus Titanosaurus, which was coined by Lydekker in 1877, on
   the basis of a partial femur and two incomplete caudal vertebrae.
   Fourteen species have since been referred to Titanosaurus, which
   distribute the genus across Argentina, Europe, Madagascar, India and
   Laos and throughout 60 million years of the Cretaceous Period. Despite
   its centrality to titanosaur systematics and biogeography, a
   re-evaluation of all Titanosaurus species recognises only five as
   diagnostic. The type species T. indicus is invalid, because it is based
   on 'obsolescent' characters - once diagnostic features that have gained
   a broader taxonomic distribution over time. Consequently, use of the
   genus Titanosaurus has largely been abandoned. The most well known
   Titanosaurus specimens have since been re-assigned to other genera,
   including Isisaurus. However, if Titanosaurus indicus is redescribed in
   the future, on the basis of new finds, Titanosaurus itself becomes
   provisionally valid.

   Some authors (like Sereno, 2005 ) contend that, since the name
   Titanosaurus is invalid, its co-ordinated rank-taxa (e.g.
   Titanosaurinae, Titanosauridae, Titanosauroidea) must be abandoned .
   However, while it is possible, under ICZN rules, to suppress family
   names, due to dubious type species, this is not typically carried out
   in practice (such families as Hadrosauridae and Ceratopsidae are also
   based on dubious genera, Hadrosaurus and Ceratops respectively).

   Normally, workers who consider all Titanosaur- names invalid promote
   Saltasaurinae and Nemegtosaurinae to family status and leave the
   remaining genera outside any family.

Taxonomy

     * Superfamily Titanosauroidea
          + Euhelopus ( Shandong, China)
          + Erketu (Mongolia)
          + Titanosauria
               o Austrosaurus ( Queensland, Australia)
               o Ligabuesaurus (Argentina)
               o Andesaurus (Argentina)
               o Bruhathkayosaurus (Southern India)
               o Family Titanosauridae
                    # Titanosaurus
                    # Epachthosaurus ( Patagonia in Argentina)
                    # Argentinosaurus (Argentina)
                    # Antarctosaurus (Argentina)
                    # Malawisaurus (Malawi, Africa)
                    # Argyrosaurus (Argentina)
                    # Gondwanatitan (Brazil)
                    # Aeolosaurus (Argentina)
                    # Baurutitan (Brazil)
                    # Trigonosaurus (Brazil)
                    # Alamosaurus (Texas, USA)
                    # Isisaurus (India)
                    # Ampelosaurus (Southern France)
                    # Magyarosaurus (Romania)
                    # Subfamily Nemegtosaurinae
                         @ Quaesitosaurus (Central Asia)
                         @ Bonitasaura (Argentina)
                         @ Rapetosaurus (Madagascar)
                         @ Nemegtosaurus (Mongolia)
                    # Subfamily Opisthocoelicaudiinae
                         @ Opisthocoelicaudia (Mongolia)
                    # Subfamily Saltasaurinae
                         @ Jainosaurus (India)
                         @ Maxakalisaurus (Brazil)
                         @ Neuquensaurus (Argentina)
                         @ Saltasaurus (Northwest Argentina & Uruguay)

Discovery in Italy

   Four well preserved skeletons of a titanosaur were found in Italy, a
   discovery first reported on May 2, 2006. Italian paleontologists say
   that this discovery will force a reassessement of current Titanosaur
   morphology.
   Retrieved from " http://en.wikipedia.org/wiki/Titanosaur"
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   with only minor checks and changes (see www.wikipedia.org for details
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