Giganotosaurus (Giant southern lizard)
Giganotosaurus (Giant southern lizard)
Named By : Rodolfo Coria & Leonardo Salgado -1995
Diet : Carnivore
Size : Estimated 12 – 13 meters long
Type of Dinosaur : Large Theropod
Type Species : G. carolinii (type)
Found in : Argentina - Candeleros Formation
When it Lived : Early Cretaceous, 112-90 million years ago
Giganotosaurus (/,dZaIg@,noUt@’so:r@s/ JY-g@-NOH-t@-SOR-@s) is a genus of theropod dinosaur that lived in what is now Argentina, during the early Cenomanian age of the Late Cretaceous period, approximately 99.6 to 97 million years ago. Nearly 70% of the holotype specimen was found in the Candeleros Formation in Patagonia in 1993. Giganotosaurus carolinii was given the name in 1995. The genus name means “giant southern Lizard”, and the specific name is in honor of Ruben D. Carolini, the animal’s discoverer. This animal was later given a dentary bone, tooth, and tracks that were discovered prior to the holotype. The scientific debate surrounding the maximum size of theropod dinosaurs centered on the genus.
Giganotosaurus was one the largest terrestrial carnivores known. However, it is difficult to estimate its exact size due to the incompletion of remains so far. The most complete specimen has a length range of 12 to 13m (39 to43 ft), a skull of 1.53 to 1.80m (5.9 to 5.9 ft), and a weight range of 4.2 to 13.8t (4.6 to 15.2 short tonnes). Extrapolating a length of 13.2m (43 feet) from the dentary bone belonging to an allegedly larger animal has been done. Researchers have determined that the animal is larger than Tyrannosaurus. However, others believe they are roughly the same size and the Giganotosaurus size estimates have been exaggerated. The skull was low with rough and wrinkled nasal bones, and a ridge-like crown on the lacrimal bone. The lower jaw had a flattened front and a downward-projecting process (or “chin”) at its tip. The serrations on the teeth were angled sideways. The pectoral girdle was proportionally small and the neck was strong.
Part of the family Carcharodontosauridae, Giganotosaurus is one of the most completely known members of the group, which includes other very large theropods, such as the closely related Mapusaurus and Carcharodontosaurus. Giganotosaurus is believed to have been homeothermic, a type of “warm bloodedness”, with a metabolism similar to that of a mammal or a reptile. This would have allowed for rapid growth. It could have run at speeds of up to 14 m/s (50 km/h, 31 mph) It could close its jaws quickly and deliver powerful bites to capture prey. It may have been able to resist stress by having a bite against prey. Giganotosaurus is believed to have been the ecosystem’s apex predator, feeding on juvenile sauropod dinosaurs.
Ruben D. Carolini, an amateur fossil hunter, discovered the tibia of a theropod dinosaur in 1993 while driving a dun buggy through the badlands of Villa El Chocon in Neuquen, Patagonia, Argentina. After being notified of this find, specialists from the National University of Comahue were dispatched to excavate and remove the specimen. After being impressed by a photograph of the leg-bone, Rodolfo Salgado and Leonardo Coria, the paleontologists announced the discovery at the 1994 Society of Vertebrate Paleontology meeting. The partial skull was found scattered across an area of approximately 10 m2 (1110 sq ft), while the postcranial bone was dissected. The specimen retained almost 70% of its skeleton. It included the entire vertebral column, most of the pelvic and pectoral girdles, as well as the femora, left tibia, and fibula. Coria and Salgado preliminarily classified this specimen (MUCPvCh1) in 1995. They made it the holotype for the new species Giganotosaurus carolinii. Parts of the skeleton were still covered in plaster at that time. The term “lizard” is derived from the Ancient Greek words gigas/gigas, notos/notos, which are both Greek words meaning “giant”, “austral/southern”, and “sauros/-sauros. Carolini was the discoverer. The name is specific. The Ernesto Bachmann Palaeontological Museum in Villa El Chocon houses the holotype skull. It was established in 1995 by Carolini. The main exhibit at the museum is the specimen. It is located on the sandy floor in a room dedicated to the animal. Paleontologists used tools during excavations. In an adjoining room, a mounted reconstruction of the skull is displayed.
Theropod dinosaurs are known for having the largest group of terrestrial predators in the Mesozoic Era. This is one of the most fascinating features. The discovery of Megalosaurus, one of the first dinosaurs to be discovered, in 1824 triggered this interest. It was named for its large size. In 1905, Tyrannosaurus was renamed. It remained the largest theropod dinosaur for more than 90 years. However, other large theropods are also known. New discoveries from Africa and South America in the 1990s revived the debate about which theropod is the largest. Coria and Salgado originally described Giganotosaurus as the largest theropod dinosaur in the southern hemisphere. It was also the largest in the entire world. Although they acknowledged that Tyrannosaurus is difficult to compare with due to the disarticulated cranial bones from Giganotosaurus’, they noted that Giganotosaurus’ femur was 5.8 m (2 ft) longer than the one of Sue, the largest Tyrannosaurus specimen. They also observed that Giganotosaurus’ bones appeared stronger, which suggests that it was a heavier animal. The skull was estimated to be approximately 1.53m (5ft) in length, while the entire animal measured 12.5m (4ft) in length, with a weight between 6 and 8 t (66.6 to 8.8 short tons).
Paul Sereno, a paleontologist, and his colleagues discovered a new skull belonging to the related genus Carcharodontosaurus. This was a theropod that had been described in 1927, but only fragmentary remains were available. The original fossils were destroyed during World War II. The skull was 1.60m (5ft) in length, which is similar to Giganotosaurus but may have been larger than Tyrannosaurus Sue’s 1.53m (5ft) skull. They pointed out that Tyrannosaurus seems to have had longer hind legs than Tyrannosaurus, and that carcharodontosaurs have the largest skulls.  Sereno stated that the newly discovered South American and African theropods competed with Tyrannosaurus for the title of “new beast usurps T. Rex as king Carnivore” in 1995. This would aid in understanding the Late Cretaceous dinosaur faunas which were otherwise very North-centric. Philip J. Currie, a paleontologist, cautioned that neither Carcharodontosaurus nor Tyrannosaurus were the larger of the two. He also noted that size is not as important to paleontologists as adaptations, relationships, distribution, and distribution. It was also remarkable to him that the two animals were found within one year of each other and were very closely related, despite being on different continents.
Coria stated that Giganotosaurus was 13.7 (45 ft.) to 14.3 (44.7 ft.) m in length and weighed 8-10 t (8.8-11.0 short tons) based upon new material. This figure is larger than Carcharodontosaurus. Sereno countered, stating that it was difficult to establish a range of size for a species from a few incomplete specimens. Both paleontologists agreed that other aspects were more important than the “size contest”. Jorge O. Calvo, a paleontologist, and Coria gave a partial left dentary bone (partially of the lower jaw) to Giganotosaurus in 1998. Calvo had found it near Los Candeleros in 1988. He briefly described it in 1989. However, he suggested that it might have been a new taxon of theropods. Calvo and Coria found that the dentary was identical to the holotype specimen, but 8% larger at 62.5 cm (24 in). Although the rear portion of it is not complete, they suggested that the skull length of the holotype specimen was 1.80m (6 ft), and that the skull length of the larger specimen was 1.95m (6.4ft), making it the longest skull of any theropod.
Calvo referred a missing tooth (MUCPv-52) to Giganotosaurus in 1999. This specimen was found near Lake Ezequiel Ramos Mexia by A. Delgado in 1987 and is the first fossil of the genus. Calvo suggested that Giganotosaurus owned some of theropod tracks and isolated tracks, which he used as the basis for the ichnotaxon Abelichnus Astigarrae in 1991. The longest track is 50 cm (20in) in length and has a speed of 130 cm (51in). The smallest track is 36 cm (14.1 in) in length with a speed of 100 cm (33.9 in). The tracks are tridactyl, which means three-toed. They have large and coarse claw impressions and have large digits. The track length is almost all taken up by impressions of the digits. One track also has a narrow heel. The tracks were found at a stratigraphic higher level than the main fossils from Giganotosaurus. However, they were also from the same strata that the single tooth and several sauropod dinosaurs from the same area as Giganotosaurus.
Frank Seebacher, a physician-scientist, proposed a new polynomial way of estimating body-mass for dinosaurs. This method used body-length, width, and depth to calculate the weight of Giganotosaurus. It was based on an original 12.5 m (41 feet) length estimate. Coria and Currie described the braincase of Giganotosaurus in 2002. They gave a length estimation of 1.60m (5ft) for the holotype head. Currie then calculated a weight estimate of 4.2t (4.6 short tons), extrapolating from the circumference of Giganotosaurus’ femur-shaft at 520mm (20in). The encephalization ratio (a measure of relative brain sizes) was 1.9. Gerardo V. Mazzetta, a paleontologist, and his colleagues noted that the Giganotosaurus Holotype’s femur was larger than the one of “Sue”, but that the tibia measured 8 cm (3 inches) shorter at 1.12m (4 ft). The holotype specimen was equal in size to Tyrannosaurus at 8 t (8.8 small tons) (marginally less than “Sue”) but the dentary could have represented an animal of 10 to 11 short tons, if it were geometrically similar to the Holotype specimen. These authors used multivariate regression equations to suggest a weight alternative of 6.5 t (7.2 short tons) in the holotype specimen and 8.2 tonnes (9.0 short tons), for the larger specimen. The latter was the largest terrestrial carnivore.
Cristiano Dal Sasso, a paleontologist, and his colleagues discovered new skull material (a nose) from Spinosaurus in 2005. These original fossils were destroyed during World War II. They concluded that this dinosaur was 16-18 m long (52-59 ft) and weighed 7-9 t (7.7-9.9 short tons), which is larger than any other theropod. Coria Currie and Currie described in 2006 the large theropod Mapusaurus of Patagonia. It was very similar to Giganotosaurus, and approximately the same size. Francois Therrien (paleontologist) and Donald M. Henderson (palaeontologist) found that Giganotosaurus (44 feet) and Carcharodontosaurus (13.0 t (15.2 short tonnes) would have both exceeded Tyrannosaurus’s lengths. They also estimated the Giganotosaurus Holotype skull to be 1.56 meters (5 feet) long. These measurements were dependent on the accuracy of the skull reconstructions. More complete specimens are needed to make more precise estimates. They found that the reconstruction of Spinosaurus by Dal Sasso (and others) was too large. Instead, they estimated that it measured 14.3m (47 feet) in length, weighed 20.9t (23.0 short tonnes), and could have been as low as 12.6m (41 feet) in height and 12t (13 short tons). These dinosaurs were larger than a strictly bipedal animal and they had exceeded the biomechanical limit. Gregory S. Paul, a paleontologist, suggested in 2010 that the skulls of carcharodontosaurs were too long.
Matthew T. Carrano, a paleontologist, and his colleagues noticed that Giganotosaurus was getting a lot of attention because of its size and that, despite the holotype being fairly complete, it hadn’t been detailed beyond the braincase. The skull’s length was ambiguous because of the lack of preservation of many skull bone contacts. Instead, they found that the skulls of Giganotosaurus (and Carcharodontosaurus) were the same size as Tyrannosaurus’s. The Giganotosaurus Holotype’s femur was also measured at 1.365m (4 feet) in length. This is in direct contrast to the original measurement. They suggested that the overall body mass would have been lower. Scott Hartman, a paleontologist, published a Graphic Double Integration mass estimation (based on drawn bone reconstructions) on his blog in 2013. He found that Tyrannosaurus (“Sue”) was larger than Giganotosaurus overall. The Giganotosaurus Holotype was estimated to have weighed 6.8 tonnes (7.5 short tons), while the larger specimen was 8.2 tonnes (9.0 short tons). Hartman estimated Tyrannosaurus to have weighed 8.4 tonnes (9.3 short tons). Hartman also noted that the larger specimen was slightly longer than the smaller one, but they looked similar from a side view. Hartman also noted that the Giganotosaurus’ dentary, which was supposed to be 8% larger than the holotype specimen, could have been 6.5% smaller or simply belong to an animal of similar size with a stronger dentary. Although there is only one known good Giganotosaurus specimen, it is possible to find larger ones, given the time it took to discover Tyrannosaurus.
Nizar Ibrahim and his colleagues in 2014 estimated that Spinosaurus was over 15m (49 feet) long, using extrapolations from a new specimen. This was done by extrapolating to match the Dal Sasso- and co-workers’ snout. This would make Spinosaurus, the largest carnivorous dinosaur known. W. Scott Persons and his colleagues, paleontologists, described a Tyrannosaurus species (nicknamed “Scotty”) in 2019. They estimated that it was larger than other giant theropods. However, they cautioned that the femoral proportions for the carcharodontosaurids Giganotosaurus, Tyrannotitan, indicated that it had a greater body mass than any other adult Tyrannosaurus. These theropods were not known to have been found by as many specimens as Tyrannosaurus. Future finds could reveal larger specimens, as shown by the large Giganotosaurus toothary. The femoral circumference of “Scotty”, which was the largest, was approximately 10% less than Giganotosaurus’s. However, it was hard to compare the proportions among large theropod groups.