Giganotosaurus: Facts About the 'Giant Southern Lizard'

Giganotosaurus was one of the largest meat-eating dinosaurs. It roamed the swamp lands of South America at the end of the Mesozoic Era, about 97 million years ago.

For a long time, Tyrannosaurus rex — "king of the dinosaurs" — was thought to be the largest land-based carnivorous dinosaur. However, T. rex has been dethroned; Giganotosaurus is now believed to have had a slight edge. And while Giganotosaurus certainly was a giant among dinosaurs, it ranks behind Spinosaurus in size among the meat-eating dinosaurs.

Giganotosaurus vs. Spinosaurus vs. Tyrannosaurus

None of these dinosaurs lived at the same time — or in the same area. Here is a comparison:

  Giganotosaurus Spinosaurus Tyrannosaurus
Lived 97 mya in South America 112-97 mya in North Africa 67 to 65 mya in North America and Mongolia
Lgth. 40-46 feet 41 to 59 feet 40 feet
Wt. 8 tons Up to 23 tons 6-8 tons
Body Huge skull with sharp teeth; powerful arms with three-fingered hands with claws Long spines on back; long, narrow snout; powerful jaws with needle-like teeth Strong back legs; tiny forearms; massive, thick skull; powerful jaws with serrated teeth

But even Spinosaurus was dwarfed by the largest dinosaur, an herbivore named Argentinosaurus, which measured as much as 140 feet (43 meters) long and weighed up to 90 tons (82 metric tons).

Big, strong and fast

Pronounced jig-a-NOT-o-SOR-us, the name is Greek for "giant southern lizard." It is a member of the Carcharodontosaurid ("shark-toothed lizards") family of dinosaurs and lived about 97 million years ago during the early Cenomanian stage of the Late Cretaceous Period. It is estimated that it became extinct at the end the Mesozoic Era, which has been called the "Age of the Dinosaurs." Giganotosaurus lived about 30 million years before T. rex.

Paleontologists estimate that Giganotosaurus measured between 40 feet and 46 feet (12.2 meters and 13 meters) from head to tail, 23 feet (7 m) from the ground to the top of its head and 12 feet (3.6 m) at its hip.

Original weight estimates put the dinosaur at between 6.5 tons and 13.3 tons (5,897 kilograms and 12,065 kilograms). Some scientists now question the accuracy of that original weight assessment and put it closer to 8 tons (7,257 kg).

Giganotosaurus walked upright on two large and powerful back legs. It is believed to have been fairly agile, thanks to its thin, pointed tail that may have provided balance and the ability to make quick turns even when running at top speed. It is estimated that Giganotosaurus could travel at speeds of up to 31 mph (50 kph), making it relatively fast for an animal its size.

Giganotosaurus' head alone was larger than most adult humans, but it is thought that it had a relatively small brain. This dinosaur had the longest skull of any known theropod, measuring between 5.9 feet and 6.6 feet (1.8 m to 2 m) in length. It had openings on the edges of its snout and above its eyes. The back of the skull had a steep forward incline, bringing the jaw joints far behind the attachment point of its long neck.

It had two short yet powerful arms with sharp claws on the end of its three-fingered "hands" as well as its feet. Coupled with its large, strong jaw, it could easily grip and rip through its prey.

The dagger-like 8-inch teeth of Giganotosaurus were short and narrow with serrated edges, providing for easy slicing of flesh. Its mandibula was reinforced with a "chin" and widened to accommodate prey.

What did Giganotosaurus eat?

Scientists believe that Giganotosaurus survived mostly on large herbivore dinosaurs. Because of its size, it did not have any natural predators.

Unlike T. rex, who feasted mostly on other animals that were already dead, Giganotosaurus had the capability of killing live prey. While scientists believe Giganotosaurus feasted mostly on live prey, it is also possible it was a scavenger when the supply of live food was tight.

Fossils of Mapusaurus, a relative of Giganotosaurus, have been found grouped closely together. This discovery points to the dinosaurs hunting in packs, a behavior that could possibly have extended to Giganotosaurus.

As fossils of larger herbivore dinosaurs such as the Antarctosaurus were found near Giganotosaurus, it is presumed they were its prey.

Fossil finds

Giganotosaurus was discovered not by a paleontologist but by Rubén Dario Carolini, a local auto mechanic and amateur dinosaur hunter. The species name, Giganotosaurus carolinii, honors him.

Carolini discovered the skeleton in July 1993 in deposits of Patagonia in southern Argentina in a region that is now referred to as the Candeleros Formation. The skeleton was about 70 percent complete and included the skull, pelvis, leg bones and most of the backbone.

A second, more fragmented specimen of the Giganotosaurus has also been identified. Found in 1987 by Jorge Calvo, it only includes the front part of the left lower jaw.

While the remains of many other dinosaurs have been discovered at various stages of development — young, juveniles and full-grown adults — there is a lack of Giganotosaurus fossils to be studied. Scientists believe that due to the fact that Giganotosaurus had no enemies, the majority of animals lived to old age or died of natural causes. No complete skeleton of a Giganotosaurus has been found.  

Giganotosaurus was named in 1995 by Rodolfo Coria, a paleontologist from the Carmen Funes Museum in Neuquen, Argentina. Giganotosaurus should not be confused with Gigantosaurus, a lesser known dinosaur found in England.

Infographic: Dinosaur profile of the giant carnivorous dinosaur Giganotosaurus.


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Kim Ann Zimmermann

Kim Ann Zimmermann is a contributor to Live Science. She holds a bachelor’s degree in communications from Glassboro State College.
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