Giganotosaurus

Introduction

The longest meat-eating dinosaur yet discovered is Giganotosaurus, a 44-46 ft (13.5-14.3 m) long behemoth, who weighed about 8 tons and stood 12 feet tall (at the hips). It walked on two legs, had a brain the size of a banana, and had enormous jaws with 8-inch long serrated teeth in a 6-foot (1.8 m) long skull. Giganotosaurus was a theropod from the mid-Cretaceous, living about 100-95 million years ago, toward the end of the Mesozoic Era, the “Age of Reptiles”.

Giga-noto-saurus means “giant southern reptile”. Its fossil was unearthed in Argentina in 1994. 70 percent of the skeleton has been found. Near the Giganotosaurus, fossils were found of 75-foot-long plant eaters, presumably victims of this Giganotosaurus.

Size

Giganotosaurus was probably bigger than Tyrannosaurus rex, who was about 40-50 feet long, about 5 tons in weight and about 10 feet tall at the hips. Giganotosaurus, however, was more lightly built and had a much smaller brain case.

When it Lived

Giganotosaurus lived about 95 million years ago, during the late Cretaceous period. This was about 30 million years before Tyrannosaurus rex, which was among the last of the dinosaur species alive before the Cretaceous-Tertiary extinction 65 million years ago.

Fossils

Rodolfo Coria, a paleontologist from the Carmen Funes Museum in Neuquen, Argentina, excavated the Giganotosaurus from the Patagonia region of Argentina (in southern Argentina), which was originally (in 1994) found by a local auto mechanic whose hobby is hunting dinosaur bones. In honor of the discoverer, Ruben Carolini, the huge dinosaur has been named Giganotosaurus carolinii. It was named by Coria and Salgado in 1995.

A Comparison of Giganotosaurus and T. rex

	Giganotosaurus carolinii	Tyrannosaurus rex
Skull length	6 feet (1.8 m)	5 feet (1.5 m)
Hands	3 fingers	larger, with 2 fingers
Height at hips	12 feet (3.7 m)	10 feet (3 m)
Length	43 ft (13 m)	40 feet (12 m)
Weight	about 8 tons	about 5 tons
Teeth	long, knife-like, serrated - slicing action	conical, serrated - crushing action
Brain size, shape	small, banana shaped	larger and wider
When they lived	about 100-95 million years ago	about 65 million years ago
Where they lived	South America	North America
Picture

Classification

Giganotosaurus was a theropod dinosaur. The theropods were a suborder of the Order Saurischia, the lizard-hipped dinosaurs.

Locomotion

Giganotosaurus walked on two legs, and may have been a relatively fast dinosaur. Its slim, pointed tail may have provided balance and quick turning while running. Dinosaur speeds are estimated using their morphology (things like leg length and estimated body mass) and fossilized trackways (which have not been found yet for Giganotosaurus). Unlike old depictions of theropods, Giganotosaurus must have held its tail erect, and did not drag it on the ground.

There has been some debate, though, on whether or not the massive, short-armed theropods (like T. rex, Giganotosaurus, Albertosaurus, and Allosaurus) could run very fast because if they fell, their short arms would not break their fall and they would be badly injured (James Farlow, 1995). This meant that these large theropods were slow, lumbering animals.

Dr. Bruce Rothschild, of the Arthritis Center of Northeast Ohio, has found evidence of 14 fractured ribs in an Allosaurus that reflect healed injuries that were probably received in falls. These were most likely bellyflops that happened while running while running (as reported in the April 16, 1998 New Scientist).

An x-ray analysis of the Allosaurus fossil indicated that the Allosaurus ribs near the scapula (the shoulder bone) were cracked and had healed. The Allosaurus was capable of recovering after many severe forwards tumbles that probably occurred while it was running. So the suggestion that perhaps the large short-armed theropods were not capable of running because they couldn’t recover after a fall apparently wasn’t so, at least for Allosaurus - this Allosaurus did recover many times after bad tumbles.

In 1995 James Farlow of Indiana-Purdue University argued that a large T. rex could run no faster than 20 mph (32 kph), because if it did, a fall would probably be so severe as to kill it. T. rex weighed about 6 tons and was up to 20 feet (6 m) tall but Allosaurus was slightly smaller, about 3 tons and 16.5 feet (5 m) long. Farlow says that Rothschild’s analysis is consistent with his theory since Allosaurus was smaller than T. rex (its smaller mass would make the impact much less powerful so the animal may have been able to recover after a running fall). Giganotosaurus and T. rex were quite similar in size, so Giganotosaurus may or may not have been a fast runner.

Printouts

• A printout on Giganotosaurus
• Print out a K-3 level Giganotosaurus information page to color!
• Giganotosaurus fact sheet