Giganotosaurus
Giganotosaurus | |
---|---|
Reconstructed skeleton, possibly with a proportionally too long skull, Fernbank Museum of Natural History | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | Saurischia |
Clade: | Theropoda |
Family: | †Carcharodontosauridae |
Tribe: | † Giganotosaurini
|
Genus: | †Giganotosaurus Coria & Salgado, 1995[1] |
Species: | †G. carolinii
|
Binomial name | |
†Giganotosaurus carolinii Coria & Salgado, 1995
|
Giganotosaurus (
Giganotosaurus was one of the
Part of the family
Discovery
In 1993, the amateur Argentine
In 1995, this specimen was preliminarily described by Coria and Salgado, who made it the holotype of the new genus and species Giganotosaurus carolinii (parts of the skeleton were still encased in plaster at this time). The generic name is derived from the Ancient Greek words gigas/γίγας (meaning "giant"), notos/νότος (meaning "austral/southern", in reference to its provenance) and -sauros/-σαύρος (meaning "lizard"). The specific name honors Carolini, the discoverer.[1][7] The holotype skeleton is now housed in the Ernesto Bachmann Paleontological Museum (where it is catalogued as specimen MUCPv-Ch1) in Villa El Chocón, which was inaugurated in 1995 at the request of Carolini. The specimen is the main exhibition at the museum, and is placed on the sandy floor of a room devoted to the animal, along with tools used by paleontologists during the excavation. A mounted reconstruction of the skeleton is exhibited in an adjacent room.[4][8]
One of the features of theropod dinosaurs that has attracted most scientific interest is the fact that the group includes the largest terrestrial predators of the
In 1996, the paleontologist Paul Sereno and colleagues described a new skull of the related genus Carcharodontosaurus from Morocco, a theropod described in 1927 but previously known only from fragmentary remains (much of its fossils were destroyed in World War II). They estimated the skull to have been 1.60 m (5 ft) long, similar to Giganotosaurus, but perhaps exceeding that of the Tyrannosaurus "Sue", with a 1.53 m (5 ft) long skull. They also pointed out that carcharodontosaurs appear to have had the proportionally largest skulls, but that Tyrannosaurus appears to have had longer hind limbs.[9] In an interview for a 1995 article entitled "new beast usurps T. rex as king carnivore", Sereno noted that these newly discovered theropods from South America and Africa competed with Tyrannosaurus as the largest predators, and would help in the understanding of Late Cretaceous dinosaur faunas, which had otherwise been very "North America-centric".[10] In the same issue of the journal in which Carcharodontosaurus was described, the paleontologist Philip J. Currie cautioned that it was yet to be determined which of the two animals were larger, and that the size of an animal is less interesting to paleontologists than, for example, adaptations, relationships, and distribution. He also found it remarkable that the two animals were found within a year of each other, and were closely related, in spite of being found on different continents.[11]
In a 1997 interview, Coria estimated Giganotosaurus to have been 13.7 (45 ft) to 14.3 (47 ft) m long and weighing 8 to 10 t (8.8 to 11.0 short tons) based on new material, larger than Carcharodontosaurus. Sereno countered that it would be difficult to determine a size range for a species based on few, incomplete specimens, and both paleontologists agreed that other aspects of these dinosaurs were more important than settling the "size contest".
In 1999, Calvo referred an incomplete tooth, (MUCPv-52), to Giganotosaurus; this specimen was discovered near Lake Ezequiel Ramos Mexia in 1987 by A. Delgado, and is therefore the first known fossil of the genus. Calvo further suggested that some theropod trackways and isolated tracks (which he made the basis of the
Continued size estimations
In 2001, the
In 2005, the paleontologist
In 2012, the paleontologist Matthew T. Carrano and colleagues noted that though Giganotosaurus had received much attention due to its enormous size, and in spite of the holotype being relatively complete, it had not yet been described in detail, apart from the braincase. They pointed out that many contacts between skull bones were not preserved, which lead to the total length of the skull being ambiguous. They found instead that the skulls of Giganotosaurus and Carcharodontosaurus were exactly the same size as that of Tyrannosaurus. They also measured the femur of the Giganotosaurus holotype to be 1.365 m (4 ft) long, in contrast to the original measurement, and proposed that the body mass would have been smaller overall.[22] In 2013, the paleontologist Scott Hartman published a Graphic Double Integration mass estimate (based on drawn skeletal reconstructions) on his blog, wherein he found Tyrannosaurus ("Sue") to have been larger than Giganotosaurus overall. He estimated the Giganotosaurus holotype to have weighed 6.8 t (7.5 short tons), and the larger specimen 8.2 t (9.0 short tons). Tyrannosaurus was estimated to have weighed 8.4 t (9.3 short tons), and Hartman noted that it had a wider torso, though the two seemed similar in side view. He also pointed out that the Giganotosaurus dentary that was supposedly 8% larger than that of the holotype specimen would rather have been 6.5% larger, or could simply have belonged to a similarly sized animal with a more robust dentary. He conceded that with only one good Giganotosaurus specimen known, it is possible that larger individuals will be found, as it took most of a century to find "Sue" after Tyrannosaurus was discovered.[23]
In 2014, the paleontologist Nizar Ibrahim and colleagues estimated the length of Spinosaurus to have been over 15 m (49 ft), by extrapolating from a new specimen scaled up to match the snout described by Dal Sasso and colleagues.[24] This would make Spinosaurus the largest known carnivorous dinosaur.[25] In 2019, the paleontologist W. Scott Persons and colleagues described a Tyrannosaurus specimen (nicknamed "Scotty"), and estimated it to be more massive than other giant theropods, but cautioned that the femoral proportions of the carcharodontosaurids Giganotosaurus and Tyrannotitan indicated a body mass larger than other adult Tyrannosaurus. They noted that these theropods were known by far fewer specimens than Tyrannosaurus, and that future finds may reveal specimens larger than "Scotty", as indicated by the large Giganotosaurus dentary. While "Scotty" had the greatest femoral circumference, the femoral length of Giganotosaurus was about 10% longer, but the authors stated it was difficult to compare proportions between large theropod clades.[26][27]
In 2021, the paleontologist Matías Reolid and colleagues compiled various mass estimates of theropods (including Giganotosaurus) to calculate the average, but did not include Therrien and Henderson's 2007 estimates of Carnotaurus and Giganotosaurus, considering them outliers. This resulted in a body mass range for Giganotosaurus between 5.5 and 8.5 t (6.1 and 9.4 short tons), with an average of 6.75 t (7.44 short tons). They also applied the skull length and body length ratio proposed by Therrien and Henderson and reconstructed various digital 3D models of theropods to measure body mass distribution and volume, resulting in the mass of a 13 m (43 ft) long Giganotosaurus up to 7.2 t (7.9 short tons). These researchers found the estimates consistent with the values proposed by previous studies.
Description
Giganotosaurus is thought to have been one of the largest theropod dinosaurs, but the incompleteness of its remains have made it difficult to estimate its size reliably. It is therefore impossible to determine with certainty whether it was larger than Tyrannosaurus, for example, which has been considered the largest theropod historically. Different size estimates have been reached by several researchers, based on various methods, and depending on how the missing parts of the skeleton have been reconstructed. Length estimates for the holotype specimen have varied between 12 and 13 m (39 and 43 ft), with a skull between 1.53 and 1.80 m (5.0 and 5.9 ft) long, a femur (thigh bone) between 1.365 and 1.43 m (4.48 and 4.69 ft) long, and a weight between 4.2 and 13.8 t (4.6 and 15.2 short tons).[6][1][13][20] Fusion of sutures (joints) in the braincase indicates the holotype specimen was a mature individual.[6] A second specimen, consisting of a dentary bone from a supposedly larger individual, has been used to extrapolate a length of 13.2 m (43 ft), a skull 1.95 m (6.4 ft) long, and a weight of 8.2 t (9.0 short tons). Some writers have considered the largest size estimates for both specimens exaggerated.[13][31][23][22] Giganotosaurus has been compared to an oversized version of the well-known genus Allosaurus.[10]
Skull
Though incompletely known, the skull of Giganotosaurus appears to have been low. The
The
The dentary of the lower jaw expanded in height towards the front (by the
Postcranial skeleton
The neck of Giganotosaurus was strong, and the
The
Classification
Coria and Salgado originally found Giganotosaurus to group more closely with the theropod
As more carcharodontosaurids were discovered, their interrelationships became clearer. The group was defined as all allosauroids closer to Carcharodontosaurus than Allosaurus or
The following cladogram shows the placement of Giganotosaurus within Carcharodontosauridae according to Sebastián Apesteguía et al., 2016:[38]
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Evolution
Coria and Salgado suggested that the
Paleobiology
In 1999, the paleontologist Reese E. Barrick and the geologist William J. Showers found that the bones of Giganotosaurus and Tyrannosaurus had very similar
In 2001, the physicist Rudemar Ernesto Blanco and Mazzetta evaluated the
A 2017 biomechanical study of the running ability of Tyrannosaurus by the biologist William I. Sellers and colleagues suggested that skeletal loads were too great to have allowed adult individuals to run. The relatively long limbs, which were long argued to indicate good running ability, would instead have mechanically limited it to walking gaits, and it would therefore not have been a high-speed
Feeding
In 2002, Coria and Currie found that various features of the rear part of the skull (such as the frontwards slope of the occiput and low and wide occipital condyle) indicate that Giganotosaurus would have had a good capability of moving the skull sideways in relation to the front neck vertebrae. These features may also have been related to the increased mass and length of the jaw muscles; the jaw articulation of Giganotosaurus and other carcharodontosaurids was moved hindwards to increase the length of the jaw musculature, enabling faster closure of the jaws, whereas tyrannosaurs increased the mass of the lower jaw musculature, to increase the power of their bite.[6]
In 2005 Therrien and colleagues estimated the relative
The first known fossils of the closely related Mapusaurus were found in a
Paleoenvironment
Giganotosaurus was discovered in the
Giganotosaurus was probably the apex predator in its ecosystem. It shared its environment with herbivorous dinosaurs such as the
References
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- ^ Pons, M. "El Chocón Dinosaurs Museum". InterPatagonia. Retrieved November 14, 2016.
- ^ S2CID 39658297.
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- ^ a b c d Calvo, J. O.; Coria, R. A. (1998). "New specimen of Giganotosaurus carolinii (Coria & Salgado, 1995), supports it as the largest theropod ever found". Gaia. 15: 117–122.
- ^ a b c Calvo, J. O. (1999). "Dinosaurs and other vertebrates of the Lake Ezequiel Ramos Mexía area, Neuquén-Patagonia, Argentina". National Science Museum Monographs. 15: 13–45.
- ^ Calvo, J.O. (1990). "Un gigantesco theropodo del Miembro Candeleros (Albiano–Cenomaniano) del la Formación Río Limay, Patagonia, Argentina". VII Jornadas Argentinas de Paleontología de Vertebrados. Ameghiniana (in Spanish). 26: 241.
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- ^ a b c d Coria, R.A.; Currie, P.J. (2006). "A new carcharodontosaurid (Dinosauria, Theropoda) from the Upper Cretaceous of Argentina". Geodiversitas. 28 (1): 71–118.
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- ^ a b Hartman, S. (2013). "Mass estimates: North vs South redux". Scott Hartman's Skeletal Drawing.com. Retrieved August 24, 2013.
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- ^ Greshko, M. (2019). "World's biggest T. rex discovered". National Geographic. Archived from the original on March 26, 2019. Retrieved March 29, 2019.
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- ^ Coria, Rodolfo A.; Salgado, Leonardo (June 1996). "Dinosaurios carnívoros de Sudamérica". Investigación y Ciencia (in Spanish) (237): 39–40.
- ^ Barrick, R.E.; Showers, W.J. (1999). "Thermophysiology and biology of Giganotosaurus: Comparison with Tyrannosaurus". Palaeontologia Electronica. 2 (2). Archived from the original on May 17, 2011. Retrieved February 6, 2016.
- ^ 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.
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- ^ Therrien, F.; Henderson, D. M.; Ruff, C. B., 2005, "Bite Me: Biomechanical models of theropod mandibles and implications for feeding". In: Carpenter, K., The Carnivorous Dinosaurs. Life of the Past. Indiana University Press. pp. 179–237
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External links
- Data related to Giganotosaurus at Wikispecies
- Media related to Giganotosaurus at Wikimedia Commons
- Canadian Museum of Nature: "Who was the ultimate dino? Giganotosaurus or T. rex?" – video presented by Jordan Mallon