Was Tyrannotitan bigger than Giganotosaurus

Reconstruction of the skull
Live reconstruction of Giganotosaurus
Size comparison with a human

Giganotosaurus is a genus of theropod dinosaur from the early Upper Cretaceous Argentina. It was one of the largest known land-dwelling carnivores in the history of the earth. It is counted to the Carcharodontosauridae, a group within the Carnosauria, and was closely related to the gigantic genera Carcharodontosaurus and Mapusaurus related. So far, a fragmentary skeleton including skull and an isolated fragmentary lower jaw have been found. These finds come from the Candeleros Formation, the oldest member of the Neuquén group, and are thus dated to the early Cenomanian. Only known species is Giganotosaurus carolinii.[1]

features

Giganotosaurus is one of the largest known theropods. About 70% of the found skeleton (holotype) has survived. Length estimates are 12.2 to 13 meters, weight estimates in most studies are between 6 and 7 tons.[2][3][4][5] The row of teeth in the upper jaw measures approx. 92 centimeters in length,[6] the thigh bone measures 136.5 centimeters in length[7]. 80% of the skull of this skeleton has survived; Length estimates vary from 1.56[5] up to 1.8 meters[8]. However, a recent study indicates that these estimates are probably too high and that the skull was just as long as the Tyrannosaurus[7]. In addition to the holotype skeleton, an isolated lower jaw is known that is 8% larger than that of the holotype specimen. Calvo and Coria (1998) suggest that this lower jaw might have belonged to a 1.95 meter long skull[8]. Mazzetta and colleagues (2004) estimate the body weight of this specimen to be 8.2 tons[9]. 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 exceeded in size, according to these researchers[9].

In comparison with Tyrannosaurus were the bones of Giganotosaurus overall more robust.[2] The teeth were shorter, more oval in cross-section, and less variable in size than those of Tyrannosaurus. Jack Horner suspects that they were adapted for cutting meat, while the round teeth of Tyrannosaurus were more suitable for biting through.[10]

Is different from other theropods Giganotosaurus among other things through the relatively deep upper jawbone (maxilla), the upper and lower edges of which run approximately parallel to each other. In addition, the square shows two pneumatic openings (foramia). The lower jaw (dental) shows at the foremost end a ventral, downward-pointing tip; a feature that is otherwise only available from Piatnitzkysaurus is known.[2][11] Other unique features have been described from the area of ​​the brain skull[6].

Paleobiology

A biomechanical study by Blanco and Mazzetta (2001) estimates the maximum speed that the animal could reach while running at 14 meters per second (50 km / h). This calculation is based on the assumption that an animal can only run fast enough to maintain its body balance. At higher speeds there would be a risk of falling, which can sometimes be fatal in very large animals due to the smaller ratio between body surface and volume; large animals, for example, have significantly less body surface area in order to cushion their body mass in the event of a fall.[12]

The skull of the found skeleton is almost completely preserved, which enables the size and shape of the brain to be reconstructed. The brain was relatively long at 27.5 centimeters, but narrow with a maximum width of 7.7 centimeters. The volume is estimated at 275 cubic centimeters. This made the brain significantly smaller than that of the coelurosaurs, such as Tyrannosaurus.[6][13]

A study by Barrick and Showers (1999) examines isotope ratios of the oxygen in the phosphate of the bones in order to derive conclusions about 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 Giganotosaurus around a homoiothermal (equally warm) animal whose metabolic rate was higher than that of today's reptiles, but lower than that of today's mammals. For an 8 tonne Giganotosaurus These researchers were able to calculate a daily food requirement of 20 kilograms of meat, which corresponds to the requirements of 3 to 4 large lions or tigers.[14]

Paleoecology

The sedimentary rocks containing the fossils of Giganotosaurus hid, belong to the Candeleros Formation and were deposited in a branched river system about 99.6 to 96 million years ago. Giganotosaurus shared its habitat with the dromaeosauridsBuitreraptor[15] as well as the sauropodsLimaysaurus, Nopcsaspondylus and Andesaurus. Finds of gigantic sauropods, as they are known from the somewhat younger Huincul Formation above the Candeleros Formation, have not yet been discovered in the Candeleros Formation. The Huincul Formation hid the remains of Argentinosaurus, possibly the largest sauropod known to date.[1]

Systematics

Giganotosaurus is classified within the Carcharodontosauridae, along with genera such as Carcharodontosaurus, Tyrannotitan and Acrocanthosaurus. His closest relative was possibly also from Argentina Mapusaurus.[16][17] Coria and Currie summarize these two genera as Giganotosaurinae[16] - however, this name is not used by later authors[18]. Instead, the name Carcharodontosaurinae is common to the genera Giganotosaurus, Mapusaurus and Carcharodontosaurus summarize.[17]

History of discovery, finds and naming

Giganotosaurus-Fossils were found in the region around the Ezequiel-Ramos-Mexía reservoir. The first find, an isolated, large tooth, was made in 1987 by A. Delgado on the shores of the lake 5 km south of the El Chocón dam. Rodolfo Coria discovered a second find in 1988, the isolated lower jaw bone (a left dental, specimen number MUCPv-95), about 50 km west of El Chocón. The third find - the well-preserved holotype skeleton (copy number MUCPv-CH-1) - was discovered by the auto mechanic and fossil collector Rubén Carolini in 1993 about 15 km south of El Chocón. This skeleton includes a fragmentary skull, parts of the spine, the full shoulder and pelvic girdle, and a thigh and lower leg; Arm and foot are missing.[1] 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 (conditionally anatomically related) state.[6] The fossils are kept in the collection of the Museo de la Universidad Nacional del Comahue.[1]

The first description of this genus was published in 1995 by Rodolfo Coria, director of the Carmen Funes Museum in Argentina, and Leonardo Salgado in the journal Nature. The generic name is made up of the Greek words gigas - "giant", notos - "South" and sauros - "Lizard" together and means "Giant Lizard of the South". The second part of the species name, carolinii, honors the discoverer of the holotype skeleton, Rubén D. Carolini.[2]

Individual evidence

  1. 1,01,11,21,3Jorge O. Calvo, 1999: Dinosaurs and other vertebrates of the Lake Ezequiel Ramos Mexia Area, Neuquen - Patagonia, Argentina. In: Proceedings of the Second Gondwanan Dinosaur Symposium, edited by Y. Tomida, T. H. Rich, and P. Vickers-Rich, pp. 13-45. National Science Museum Monographs, No. 15. Tokyo.
  2. 2,02,12,22,3Coria R. A. & Salgado L. (1995): A new giant carnivorous dinosaur from the Cretaceous of Patagonia. Nature 377: 225-226.
  3. ↑ Coria, R. A. and Currie, P. J. (2006): A new carcharodontosaurid (Dinosauria, Theropoda) from the Upper Cretaceous of Argentina. Geodiversitas, 28 (1): 71-118.
  4. ↑ Seebacher, F. 2001. A new method to calculate allometric length-mass relationships of dinosaurs. Journal of Vertebrate Paleontology 21 (1). Pp. 51-60.
  5. 5,05,1Therrien, F .; and Henderson, D. M. (2007). "My theropod is bigger than yours ... or not: estimating body size from skull length in theropods". Journal of Vertebrate Paleontology 27 (1): 108-115.
  6. 6,06,16,26,3Coria, R. A. and Currie, P. J. (2003): "The braincase of Giganotosaurus carolinii (Dinosauria: Theropoda) from the Upper Cretaceous of Argentina ". Journal of Vertebrate Paleontology 22 (4): 802-811. E-Text (PDF document, 712 KB)
  7. 7,07,1 M. T. Carrano, R. B. J. Benson, S. D. Sampson: The phylogeny of Tetanurae (Dinosauria: Theropoda). In: Journal of Systematic Palaeontology. 10, No. 2, 2012, p. 233 ([1]).
  8. 8,08,1Calvo, J. O. and Coria, R. A. (1998): New specimen of Giganotosaurus carolinii (Coria & Salgado, 1995), supports it as the largest theropod ever found. Gaia, 15: pp. 117-122.
  9. 9,09,1 G. V. Mazzetta, P. Christiansen, R. A. Farina: Giants and bizarres: body size of some southern South American Cretaceous dinosaurs. In: Historical Biology. 16, No. 2-4, 2004, pp. 71-83 ([2]).
  10. ↑ Sean Henahan: Giganotosaurus. In: Access Excellence. Retrieved October 2, 2011.
  11. ↑ T. R. Holtz, R. E. Molnar, P. J. Currie. 2004. Basal Tetanurae. In D. B. Weishampel, P. Dodson, H. Osmolska (hersg.), The Dinosauria (second edition). University of California Press, Berkeley 71-110.
  12. ↑ Blanco, R. Ernesto; Mazzetta, Gerardo V. (2001). A new approach to evaluate the cursorial ability of the giant theropod Giganotosaurus carolinii. Acta Palaeontologica Polonica 46 (2): 193-202. (PDF)
  13. ↑ Hecht, Jeff (1998). "Contenders for the crown". Earth 7 (1): 16-17.
  14. ↑ Barrick, R. E. and W. J. Showers (1999): Thermophysiology and biology of Gigantosaurus: Comparison with Tyrannosaurus. Palaeontologia Electronica 2 (2): 1-22 E-Text
  15. ↑ Peter J. Makovicky, Sebastián Apesteguía, Federico L. Agnolín: The earliest dromaeosaurid theropod from South America. In: Nature. 437, 2005, pp. 1007-1011, doi: 10.1038 / nature03996.
  16. 16,016,1Rodolfo A. Coria and Philipp J. Currie (2006): A new carcharodontosaurid (Dinosauria, Theropoda) from the Upper Cretaceous of Argentina. In: "Geodiversitas". 28. PDF
  17. 17,017,1Brusatte S. L., Benson R. B. J., Chure D. J., Xu, C. Sullivan, and D. W. E. Hone. 2009: The first definitive carcharodontosaurid (Dinosauria: Theropoda) from Asia and the delayed ascent of tyrannosaurids. Science 96: 1051-1058
  18. Giganotosaurus. In: The Paleobiology Database. Retrieved October 2, 2011.