Tyrannosaurus Rex, Warrior or Wimp?
One of the Largest Land Carnivores of All Time

Tyrannosaurus Rex, Warrior or Wimp?
One of the Largest Land Carnivores of All Time
The species Tyrannosaurus rex, is one of the most well known dinosaurs and one of the largest land carnivores of all time. It lived throughout what is now western North America.

Fossils have been found in a variety of rock formations dating back from 67 to 65.5 million years ago. It was among the last non-avian dinosaurs to exist prior to a major event that destroyed the dinosaurs.

Tyrannosaurus rex - it's the scariest, meanest, most bewitching dinosaur of them all. Children are captivated by the sheer savagery of the teeth.

Experts marvelled at the force of its bite - ten times more powerful than anything we know today.

Moviemakers made millions out of the terror it inspired. But could our picture of this monster be completely wrong?

Was T. rex in fact a slow lumbering creature, with hideously bad breath, that couldn't get anywhere close to catching a Triceratops. Was it really a scavenger that lived off the scraps left by others? Was T. rex, in fact, a wimp?

Featuring fabulous graphics and interviews with T. rex experts from around the world, Horizon looks at the new science that is challenging the legend of the dinosaur we love to hate.

Tyrannosaurus rex was one of the largest land carnivores of all time; the largest complete specimen, "Sue", measured 12.8 metres (42 ft) long, and was 4.0 metres (13.1 ft) tall at the hips.

Mass estimates have varied widely over the years, from more than 7.2 metric tons (7.9 short tons), to less than 4.5 metric tons (5.0 short tons), with most modern estimates ranging between 5.4 and 6.8 metric tons (6.0 and 7.5 short tons).

Packard et al. (2009) tested dinosaur mass estimation procedures on elephants and concluded that dinosaur estimations are flawed and produce over-estimations; thus, the weight of Tyrannosaurus could be much less than usually estimated.

Although Tyrannosaurus rex was larger than the well known Jurassic theropod Allosaurus, it was slightly smaller than some other Cretaceous carnivores, such as Spinosaurus and Giganotosaurus.

The neck of Tyrannosaurus rex formed a natural S-shaped curve like that of other theropods, but was short and muscular to support the massive head.
The forelimbs had only two clawed fingers, along with an additional small metacarpal representing the remnant of a third digit.

In contrast the hind limbs were among the longest in proportion to body size of any theropod. The tail was heavy and long, sometimes containing over forty vertebrae, in order to balance the massive head and torso.

To compensate for the immense bulk of the animal, many bones throughout the skeleton were hollow, reducing its weight without significant loss of strength.

The largest known Tyrannosaurus rex skulls measure up to 5 feet (1.5 m) in length. Large fenestrae (openings) in the skull reduced weight and provided areas for muscle attachment, as in all carnivorous theropods.

But in other respects Tyrannosaurus’ skull was significantly different from those of large non-tyrannosauroid theropods.

It was extremely wide at the rear but had a narrow snout, allowing unusually good binocular vision.

The skull bones were massive and the nasals and some other bones were fused, preventing movement between them; but many were pneumatized (contained a "honeycomb" of tiny air spaces) which may have made the bones more flexible as well as lighter.

These and other skull-strengthening features are part of the tyrannosaurid trend towards an increasingly powerful bite, which easily surpassed that of all non-tyrannosaurids. The tip of the upper jaw was U-shaped (most non-tyrannosauroid carnivores had V-shaped upper jaws), which increased the amount of tissue and bone a tyrannosaur could rip out with one bite, although it also increased the stresses on the front teeth.
The largest T. Rex was an estimated 39 ft (12 m) in total length and weighed around 10 tons. They had an elongated skull and large, spike-shaped teeth in jaws that could open to a 4-ft (122-cm) gape. 

The teeth of Tyrannosaurus rex displayed marked heterodonty (differences in shape). The premaxillary teeth at the front of the upper jaw were closely packed, D-shaped in cross-section, had reinforcing ridges on the rear surface, were incisiform (their tips were chisel-like blades) and curved backwards.

The D-shaped cross-section, reinforcing ridges and backwards curve reduced the risk that the teeth would snap when Tyrannosaurus bit and pulled.

The remaining teeth were robust, like "lethal bananas" rather than daggers; more widely spaced and also had reinforcing ridges.

Those in the upper jaw were larger than those in all but the rear of the lower jaw. The largest found so far is estimated to have been 30 centimetres (12 in) long including the root when the animal was alive, making it the largest tooth of any carnivorous dinosaur yet found.

The Cretaceous–Tertiary extinction event, which occurred approximately 65.5 million years ago (Ma) at the end of the Maastrichtian, was a large-scale mass extinction of animal and plant species in a geologically short period of time.

Widely known as the K–T extinction event, it is associated with a geological signature known as the K–T boundary, usually a thin band of sedimentation found in various parts of the world. Scientists theorize that the K–T extinctions were caused by one or more catastrophic events, such as massive asteroid impact, or increased volcanic activity.

Several impact craters and massive volcanic activity, such as that in the Deccan traps, have been dated to the approximate time of the extinction event. These geological events may have reduced sunlight and hindered photosynthesis, leading to a massive disruption in Earth's ecology.

Many researchers believe the extinction was more gradual, resulting from a combination of the events above and others including sea level and climate changes.