Giganotosaurus
Giganotosaurus was a large theropod that lived in Argentina during the Late Cretaceous period. It lived and went extinct around 98 million years ago, long before the mass extinction that ended the age of dinosaurs. Currently, there is one known species – G. carolinii.
The name Giganotosaurus means "giant southern lizard," not "gigantic lizard," as it is sometimes mistranslated. It is often mispronounced as "gigantosaurus," a confusion that likely arises because other prehistoric animals use "giganto–" in their names, such as Gigantoraptor. Giganotosaurus belonged to a group of giant predatory dinosaurs called carcharodontosaurs, close relatives of Carcharodontosaurus and Mapusaurus.
Growing over 12 m long, it was roughly comparable in size to Tyrannosaurus rex but more lightly built, with a long, low skull lined with sharp, serrated teeth. It was likely capable of bringing down large prey such as young sauropods, though it may also have fed on smaller dinosaurs or scavenged carcasses.
Discovery
In 1993, fossil hunter Rubén Carolini discovered part of a large dinosaur leg bone near Villa El Chocón in Patagonia, Argentina. Excavation of the site uncovered about 70% of a skeleton, including most of the backbone, hips, and legs, along with several pieces of the skull. The remains were named Giganotosaurus carolinii in 1995, meaning "giant southern lizard," with the species name recognising Carolini. The original fossil is now displayed in the Ernesto Bachmann Paleontological Museum in Villa El Chocón.
No complete skeleton of Giganotosaurus has been found. The known fossils come mainly from this single skeleton, with a few additional finds. A partial lower jaw, a single tooth, and several large footprints found in the same region have also been linked to the species. The skull of the main specimen is incomplete, so much of its shape is reconstructed based on close relatives such as Mapusaurus. No complete arms have been found.
Size, Anatomy, and Physical Features
Giganotosaurus is thought to have been one of the largest meat-eating dinosaurs, but because its fossils are incomplete, its exact size is uncertain. Estimates for the first discovered skeleton (the holotype) suggest it was around 12 - 13 m long and about 7 m in height, with a skull roughly 1.5 - 1.8 m long and weighing between about 4 - 14 tonnes, depending on the calculation method. Another lower jaw bone from what may have been a larger individual suggests a possible length of about 13 metres. However, some scientists believe the higher estimates are exaggerated.
The skull of Giganotosaurus was long and relatively low, with rough-textured bones and a ridge-shaped crest in front of each eye. The upper jaw was deep (meaning tall from top to bottom), and carried large, blade-like teeth with fine serrations suited for slicing through flesh rather than crushing bone. The front of the lower jaw was flattened and curved slightly downward, forming a small "chin" that may have helped strengthen the jaws during biting. Each lower jaw probably held around a dozen laterally compressed (flattened from side to side, i.e. blade-like) and slightly curved teeth. Unlike T. rex, whose skull was tall and built for bone-crushing bites, Giganotosaurus had a longer, narrower skull likely suited for quick, slashing attacks.
The body of Giganotosaurus was heavily built but proportioned differently from T. rex. It had a strong neck, a relatively small shoulder girdle (the bones that supported its arms), and powerful hind limbs. The thigh bone (femur) was thick and S-shaped, while the lower leg bone (tibia) was slightly shorter but sturdy, suggesting it could move quickly for its size. The tail was long and muscular, helping it balance its large head and body while walking or turning. Although no complete arms have been found, related species suggest they were shorter than those of earlier theropods like Allosaurus but still functional. Overall, Giganotosaurus combined great size with a body designed for speed and powerful strikes, making it one of the top predators of its time.
Biology and Behaviour
Studies of Giganotosaurus fossils suggest it was at least partly warm-blooded. Chemical analysis of its bones shows that heat was distributed evenly through the body, similar to Tyrannosaurus rex. This means it likely had a metabolism between that of reptiles and mammals - known as homeothermy - which would have supported steady body temperature, quick growth, and an active lifestyle. An adult weighing around 8 tonnes would have needed about as much energy as a 1 tonne mammalian predator, suggesting it was an active hunter rather than a sluggish animal.
Its speed and movement abilities are not well known, but research gives some clues. One study calculated that Giganotosaurus could theoretically withstand speeds of up to about 50 km/h (31 mph) before its balance and stride would fail, but this was a mechanical limit, not an estimate of its true running speed. Most scientists think that large theropods like Giganotosaurus were too heavy to run at such speeds and instead moved at a fast walking pace. Its skull and jaws were adapted for quick, slicing bites rather than crushing bone. It probably used the front of its jaws to grip and cut prey, with the small "chin" at the tip of the lower jaw helping to resist stress during bites.
Giganotosaurus is thought to have been a generalist predator, feeding on animals smaller than itself - likely including juvenile sauropods and other medium-sized dinosaurs. Evidence from related species such as Mapusaurus has led some researchers to suggest these large predators may sometimes have gathered or hunted together, though this remains uncertain.
Brain Size and Intelligence
The encephalization quotient (EQ) is a rough way of comparing an animal's brain size to its body size. It gives a general idea of how much "brainpower" an animal might have relative to others, though it's not a direct measure of intelligence. For Giganotosaurus, the EQ has been estimated at about 1.9, meaning its brain was proportionally small for its body size but typical for large predatory dinosaurs. Tyrannosaurus rex is estimated at around 2.0 to 2.4, slightly higher, suggesting it may have had somewhat greater neurological capacity for its size. For comparison, modern humans have an EQ of roughly 7.5, and dolphins about 4.0–4.5.
However, EQ values are only broad estimates - they rely on uncertain measurements of brain and body size, and brain size alone doesn't directly indicate intelligence or behaviour. As with Stegosaurus, a small brain doesn't mean the animal was poorly adapted or incapable. Giganotosaurus was perfectly suited to its role as a top predator, relying on its strength, senses, and instincts rather than complex problem-solving. EQ can tell us that it had a brain typical of a large, active hunter, but not how it actually thought or behaved.
Environment
Giganotosaurus lived around 98 million years ago during the early part of the Late Cretaceous period, in what is now northern Patagonia, Argentina. Its fossils were found in the Candeleros Formation, a layer of sandstone and siltstone formed by ancient rivers, floodplains, and wind-blown sand. This landscape would have been warm and semi-arid, with areas of open woodland, river channels, and patches of swampy ground.
Giganotosaurus was likely the top predator in this environment, living alongside large plant-eating dinosaurs such as Andesaurus and Limaysaurus, as well as smaller theropods like Buitreraptor and Ekrixinatosaurus. Other animals of the time included crocodile-like reptiles, turtles, frogs, snakes, and early mammals, showing that the ecosystem was diverse and well-developed.
References & Attributions
Image: Reconstructed Giganotosaurus skeleton at the Natural History Museum in Helsinki. - Sukram-C from Espoo, Finland, CC BY-SA 2.0, via Wikimedia Commons
Image: Life restoration of Giganotosaurus. The spines along the back and skin colouration are speculative. - Dmitry Bogdanov, Public domain, via Wikimedia Commons
Image: Size comparison of two specimens of Giganotosaurus with a human - KoprX, CC0, via Wikimedia Commons
Image: Artist's depiction of Giganotosaurus alongside other species that existed during the same period. Giganotosaurus are at the back, either side of the long-necked sauropod. - ABelov2014, CC BY 3.0, via Wikimedia Commons
