Giganotosaurus

Skelettreplikat of Giganotosaurus at the Australian Museum in Sydney

• Argentina, Neuquén Province ( Candeleros Formation)

• Giganotosaurus carolinii

Giganotosaurus is a genus of theropod dinosaur from the Early Cretaceous of Argentina.

It was one of the largest known terrestrial carnivores of the Earth's history. He is counted among the Carcharodontosauridae, a group within the Carnosauria, and was closely related to the equally gigantic genera Carcharodontosaurus and Mapusaurus.

So far, a fragmentary skeleton including skulls and an isolated fragmentary lower jaw have been found. These findings are from the Candeleros lineup, the oldest layer member of the Neuquén Group, and are thus dated to the early Cenomanian. The only known species is Giganotosaurus carolinii.

Features

Giganotosaurus is one of the largest known theropod. The skeleton found ( holotype ) is handed down to about 70%. The length estimates amount to 12.2 to 13 meters, while the weight amounts in most studies on 6-7 tons. The teeth in the upper jaw measures about 92 inches in length, the femur measures 136.5 centimeters in length. The skull of this skeleton is handed down to 80%; Length estimates vary from 1.53 to 1.56 meters. A recent study indicates, however, that these estimates are probably too high and that the skull was only as long as that of Tyrannosaurus.

Next to the holotype a skeleton found isolated mandibular is known that 2-8 % greater than that of the holotype instance. Calvo and Coria (1998) suggests that this lower jaw could have belonged to a 1.95 -meter-long skull. Mazzetta and colleagues (2004 ) estimate the body weight of this specimen to 8.2 tons. While the holotype specimen was probably smaller than the largest known skeleton of Tyrannosaurus ( " Sue " ), the lower jaw fragment would have belonged to an animal that Sue surpassed in size, these researchers.

In comparison with the bones of Tyrannosaurus, Giganotosaurus were more robust. The teeth were shorter, oval in cross-section, and its size is less variable than that of Tyrannosaurus. Jack Horner suggested that they were adapted to the cutting of meat, while the rounded teeth of Tyrannosaurus were longer suitable for biting through bone.

From other theropods Giganotosaurus distinguishes itself among other things, by the relatively low upper jaw bone (maxilla ), the performance of which the upper and lower edge approximately parallel to each other. In addition, the quadrate shows two pneumatic openings ( Foramia ). The lower jaw ( dentary ) shows at the foremost end of a ventral, downward-pointing tip; a feature that is otherwise known only Piatnitzkysaurus. The pubic symphysis is the deepest part of the dental. Other unique features have been described from the area of the skull.

Paleobiology

A biomechanical study of Blanco and Mazzetta (2001 ) estimates the maximum speed that could reach the animal while running at 14 meters per second (50 km / h). This calculation is based on the assumption that an animal can only run so fast that the maintenance of body equilibrium is given. At higher speeds, the risk of a fall would be given, which can be fatal sometimes in very large animals due to the smaller ratio between body surface area and volume; so large animals have in relation significantly less body surface to cushion their body mass in a fall.

The skull of the skeleton found is almost completely intact, allowing a reconstruction of the size and shape of the brain. However, the brain was relatively long at 27.5 inches, with a maximum of 7.7 inches width narrow. The volume is estimated at 275 cubic centimeters. Thus, the brain was significantly smaller than that of the Coelurosaurier such as Tyrannosaurus.

A study by Barrick and Showers (1999) investigated isotope ratios of oxygen in the phosphate of the bone in order to derive conclusions on the metabolism of the animal. These isotope ratios indicate how the body heat was distributed in the skeleton of the living animal. So it was with a Giganotosaurus homoiothermes (just warm ) animal whose metabolic rate was greater than the present-day reptiles, but was lower than the present-day mammals. For an 8 -ton Giganotosaurus these researchers were able to calculate a daily food requirement of 20 kilograms of meat, which would correspond to the needs 3-4 big lions or tigers.

Paleoecology

The sedimentary rocks, which hid the fossils of Giganotosaurus belong to Candeleros lineup and pitched million years ago, about 100.5 to 96.2 in a branched river system from. Giganotosaurus shared its habitat with the Dromaeosauriden Buitreraptor and sauropods Limaysaurus, Nopcsaspondylus and Andesaurus. Discoveries of giant sauropods, such as are known from the slightly younger, about the Candeleros lineup following Huincul formation have not yet been discovered in the Candeleros lineup. The Huincul lineup contained the remains of Argentinosaurus, possibly the largest known sauropod.

System

Giganotosaurus is classified within the Carcharodontosauridae, along with genres such as Carcharodontosaurus, Acrocanthosaurus and Tyrannotitan. His closest relative was possibly the most, also from Argentina Mapusaurus. Coria and Currie combine these two genres together as Giganotosaurinae - this name is not used by later authors. Instead, the name Carcharodontosaurinae is common to combine the genera Giganotosaurus, Carcharodontosaurus and Mapusaurus.

History of discovery, discoveries and naming

The fossils of Giganotosaurus were discovered in the region around the Ezequiel Ramos- Mexía reservoir.

The first Fund ( an isolated, large tooth) was made in 1987 by A. Delgado, 5 km south of the dam El Chocón on the shore of the lake. Rodolfo Coria discovered in 1988 the isolated lower jaw bones ( a left dentary, copy number MUCPv -95), about 50 km west of El Chocón.

The third fund - the well-preserved holotype skeleton ( copy number MUCPv -CH- 1) - made ​​the car mechanic and fossil collectors Rubén Carolini 1993 about 15 km south of El Chocón. This skeleton includes a fragmentary skull, parts of the spine, the full shoulder and pelvic girdles, and an upper and lower legs, but the arms and feet were missing. The skull bones were found scattered over an area of ​​about 10 square meters, while the rest of the skeleton was found in a slightly disarticulated (due in anatomical connection located ) state. The fossils are preserved in the collection of the Museo de la Universidad Nacional del Comahue.

The first description of this species was published in 1995 by Rodolfo Coria, director of the Argentine Carmen Funes Museum, and Leonardo Salgado in the journal Nature. The generic name is derived from the Greek words gigas - " Giant", notos - "South" and sauros - " lizard", together meaning " giant lizard of the South". The second part of the species name, carolinii, honors the discoverer of the holotype skeleton, Rubén D. Carolini.