Giganotosaurus


 * Not to be confused with Gigantosaurus.

Giganotosaurus (meaning 'giant southern lizard', derived from the Greek gigas/γίγας meaning 'giant', notos/νότος meaning 'south wind' and -saurus/-σαύρος meaning 'lizard') is a genus of carcharodontosaurid dinosaur that lived 98 to 96 million years ago during the early Cenomanian stage of the Late Cretaceous Period. It is one of the largest known terrestrial carnivores, slightly larger than Tyrannosaurus, but smaller than Spinosaurus. Its fossils have been found in Argentina.

Discovery and species
Giganotosaurus carolinii was named for Ruben Carolini, an amateur fossil hunter who, in 1993, discovered the fossils in deposits of Patagonia (southern Argentina) in what is now considered the Candeleros Formation. It was published by Rodolfo Coria and Leonardo Salgado in the journal Nature in 1995.

The holotype specimen's (MUCPv-Ch1) skeleton was about 70% complete and included the skull, pelvis, leg bones and most of the backbone. It is estimated around 12.2-12.5 m (40-41 ft) in length. A second, more fragmentary, specimen (MUCPv-95) has also been recovered. It is only known from a portion of the left dentary which is 8% larger than the equivalent bone from the holotype. This largest Giganotosaurus specimen is estimated to represent an individual 13.2 m (43.3 ft) long, that weighed 6.2 tons. Giganotosaurus might have had the longest known skull for a theropod dinosaur, with the holotype's skull estimated at 1.80 m (6 ft) and the second specimen's estimated at 1.95 m (6.3 ft). Giganotosaurus surpasses Tyrannosaurus rex in length by less than half a meter (the upper length estimate for T. rex is 13 m).



Paleobiology
G. carolinii was slightly larger than T. rex, but had a brain only about half as big as those of tyrannosaurids. The teeth of Tyrannosaurus were longer and wider, but more variable in size. The teeth of Giganotosaurus were shorter, less variable and narrower than those of Tyrannosaurus, and were more adapted for slicing flesh. A well-developed olfactory region means that it probably had a good sense of smell. Its skull, although large, had a slender build. Titanosaur fossils have been recovered near the remains of Giganotosaurus, leading to speculation that these carnivores may have preyed on the giant herbivores. Fossils of related carcharodontosaurids grouped closely together may indicate pack hunting, a behavior that could possibly extend to Giganotosaurus itself.

Blanco and Mazzetta (2001) estimated that Giganotosaurus might have been capable of running at speeds up to 14 metres per second (31 mph).

Classification
Giganotosaurus, along with relatives like Tyrannotitan, Mapusaurus and Carcharodontosaurus, are members of the carnosaur family Carcharodontosauridae. Both Giganotosaurus and Mapusaurus have been placed in their own subfamily Giganotosaurinae by Coria and Currie in 2006 as more carcharodontosaurid dinosaurs are found and described, allowing interrelationships to be calculated.

In museums
The original fossils of Giganotosaurus remain at the Carmen Funes Museum in Neuquen, Argentina, but replicas are common in other places, including the Australian Museum in Sydney.