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Antarctosaurus

2007 Schools Wikipedia Selection. Related subjects: Dinosaurs

   iAntarctosaurus

                        Fossil range: Late Cretaceous

               Scientific classification

   Kingdom:    Animalia
   Phylum:     Chordata
   Class:      Sauropsida
   Superorder: Dinosauria
   Order:      Saurischia
   Suborder:   Sauropodomorpha
   Infraorder: Sauropoda
   (unranked)  Titanosauria
   Genus:      Antarctosaurus
               von Huene, 1929

                                   Species

     * A. wichmannianus ( type)

                      von Huene, 1929

     * ?A. giganteus

                      von Huene, 1929

     * "A." jaxartensis

                      Riabinin, 1939

     * "A." brasiliensis

                      Arid & Vizotto, 1971

   Antarctosaurus (ant-ARK-to-SAWR-us; meaning "southern lizard") is a
   genus of titanosaurian sauropod dinosaur from the Late Cretaceous
   Period of what is now South America. It was a huge quadrupedal
   herbivore with a long neck and tail. It was possibly armored. As
   Antarctosaurus is not known from a complete skeleton and tail lengths
   are highly variable among sauropods, the true size of these animals is
   hard to extrapolate. The type species may have been over 60 feet (18
   meters) long, and a second species may have been one of the largest
   land animals ever.

Etymology

   Remains of this dinosaur were first mentioned in print in 1916,
   although they were not fully described and named until a 1929
   manuscript written by paleontologist Friedrich von Huene.
   Antarctosaurus does not refer to the continent of Antarctica, since it
   was first found in Argentina, although it does have the same
   derivation, from the Greek words anti- meaning 'opposite of', arktos
   meaning 'north' and sauros meaning 'lizard'. The generic name refers to
   the animal's reptilian nature and its geographical location on a
   southern continent.

Species of Antarctosaurus

   Several species have been assigned to Antarctosaurus over the years,
   probably incorrectly in most cases.

Antarctosaurus wichmannianus

   This is the type species of the genus, named in 1929 after the
   discoverer of its remains, geologist R. Wichmann.

   Von Huene used the name A. wichmannianus to describe a large assemblage
   of bones, which are now considered to come from the Anacleto Formation
   in Río Negro Province of Argentina, which is considered to be early
   Campanian in age or about 83-80 million years old. Several skull
   fragments were described, including a braincase and a mandible (lower
   jaw). Other bones referred to this dinosaur include neck and tail
   vertebrae, ribs, and numerous limb bones. One femur (thigh bone) is
   over 6 feet (1.85 meters) tall, which has been used to extrapolate a
   mass of about 34 metric tonnes, or nearly 75,000 pounds (Mazzetta et
   al. 2004).

   These bones were for the most part not associated with each other but
   scattered throughout the formation. Consequently, many scientists
   believe that they may not all belong to the same type of animal. In
   particular, the very square lower jaw has frequently been suggested to
   belong to a rebbachisaurid sauropod similar to Nigersaurus (Upchurch
   1999; Sereno et al. 1999; Wilson 2002). However the jaw of Bonitasaura
   is similar in overall shape and is clearly associated with titanosaur
   skeletal remains, indicating that the lower jaw may belong to
   Antarctosaurus wichmannianus after all (Apesteguía 2004). The back of
   the skull and the remainder of the skeleton are usually regarded as
   titanosaurian, although they do not necessarily belong to the same type
   of titanosaur. A. wichmannianus (minus the lower jaw) has been regarded
   as a lithostrotian, a group which includes armored titanosaurs,
   although no armor scutes were associated with its remains (Upchurch et
   al. 2004). This species has also been regarded as a possible
   nemegtosaurid titanosaur (Upchurch 1999; Apesteguía 2004; Wilson 2005).

?Antarctosaurus giganteus

   Von Huene named a second species of Antarctosaurus in 1929, which he
   called A. giganteus because of its enormous size. Very few remains are
   known of this species and it is regarded as a nomen dubium by some
   (Upchurch et al. 2004). The most famous of these bones are two gigantic
   femora, which are among the largest of any known sauropod. They measure
   about 7.75 feet (2.35 meters) in length. Extrapolating from the size of
   these bones has led to a mass estimate of approximately 69 metric
   tonnes (152,000 pounds) in one study, just a little smaller than the
   gigantic Argentinosaurus, which at nearly 73 metric tonnes (160,000
   pounds) would have been the heaviest known land animal of all time
   (Mazzetta et al. 2004).

   The bones mentioned above were recovered in Neuquén Province of
   Argentina, from the Plottier Formation, which dates to the late
   Coniacian stage of the Late Cretaceous Period, or about 87 to 85
   million years ago. The Plottier, like the younger Anacleto, is a member
   of the Neuquén Group.

   As so little is known of this animal, and because the material assigned
   to A. wichmannianus is so confused, A. giganteus cannot be confidently
   assigned to the genus Antarctosaurus at this time.

"Antarctosaurus" septentrionalis

   In 1933, von Huene and Charles Matley described another species from
   India. This species does preserve important anatomical information but
   does not belong to Antarctosaurus. It was renamed Jainosaurus in 1994.

"Antarctosaurus" jaxartensis

   A single femur from Kazakhstan forms the basis of this species, which
   was named by Soviet paleontologist Anatoly Riabinin in 1939. It is
   regarded as a nomen dubium today but is almost certainly not a species
   of the South American Antarctosaurus (Upchurch et al. 2004).

"Antarctosaurus" brasiliensis

   Remains of this dinosaur, including two fragmentary limb bones and a
   partial vertebra, were found in the Bauru Formation of Brazil and
   described by Arid and Vizzotto in 1971. This species is also considered
   a nomen dubium (Upchurch et al. 2004).
   Retrieved from " http://en.wikipedia.org/wiki/Antarctosaurus"
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