TYRANNOSAURUS REX FACTS

Ask any mildly disruptive child what their favourite dinosaur is and you will invariably get the same answer - the Tyrannosaurus rex. I will of course accept that are other dinosaur species available, but for the benefit of this article it's T-rex all the way. And why wouldn't it be? Every single film from the 1933 stop-motion movie 'King Kong' to the very latest computer generated effect extravaganza has a Tyrannosaurus Rex as a lead character. If they haven't, then they have a species so similar to a T rex that you have to question why the producers bothered with the change. Example, the Carnotaurus in Disney's 'Dinosaur'. So, if you are looking for someone to blame for the T. rex's popularity, look at the filmmakers.

But what exactly do we know about the Tyrannosaurus rex?

Well, as far as we can know anything about an extinct animal, what we do know is collection of well crafted assumptions based on relatively few facts. And of course, these assumptions are still being honed. Remember this one...

'...the T-rex's visual acuity is based on movement...'

Luckily, more than 30 specimens of Tyrannosaurus rex have been identified, some of which are nearly complete skeletons. More interestingly, soft tissue and proteins have been reported in at least one of these specimens. This abundance of fossil material has allowed significant research into many aspects of the Tyrannosaurus rex's biology, including life history and bio-mechanics. The feeding habits, physiology and potential speed of Tyrannosaurus rex are just a few of the subjects still up for debate.

To make it simple to absorb, I am going to list what we know as bullet points.

1. To begin with, the name Tyrannosaurus means "tyrant lizard", from Greek tyrannos meaning "tyrant," and sauros meaning "lizard". Rex means "king" in Latin.

2. Going by size, the Tyrannosaurus rex was the largest known tyrannosaurid and one of the largest known land predators. The most complete specimen measuring up to 12.3 m in length, up to 4 metres tall at the hips, and up to 6.8 metric tons in weight.

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3.A 2012 study performed by scientists Karl Bates and Peter Falkingham of the University of Liverpool suggested that the bite force of Tyrannosaurus could have been the strongest bite force of any terrestrial animal that has ever lived.

The calculations suggested that adult T. rex could have generated from 35000 to 57000 Newtons of force in the back teeth, or the equivalent of three times the force estimated for a great white shark, 15 times the force of an African lion, 3 and a half times the force of an Australian saltwater crocodile and around 7 times the estimated force for Allosaurus.

However, even higher estimates were made by professor Mason B. Meers of the University of Tampa in 2003. In his study, Meers estimated a possible bite force of around 183000 to 235000 Newtons or 18.3 to 23.5 metric tons; a bite force equivalent to that of the largest Megalodon shark specimens.

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4. Like many bipedal dinosaurs, Tyrannosaurus rex was historically depicted as a 'living tripod', with the body at 45 degrees or less from the vertical and the tail dragging along the ground, similar to a kangaroo. This concept dates from Joseph Leidy's 1865 reconstruction of Hadrosaurus, the first to depict a dinosaur in a bipedal posture.

Henry Fairfield Osborn, former president of the American Museum of Natural History (AMNH) in New York City, who believed the creature stood upright, further reinforced the notion after unveiling the first complete Tyrannosaurus rex skeleton in 1915. It stood in this upright pose for 77 years, until it was dismantled in 1992.

By 1970, scientists realized this pose was incorrect and could not have been maintained by a living animal, as it would have resulted in the dislocation or weakening of several joints, including the hips and the articulation between the head and the spinal column. The inaccurate AMNH mount inspired similar depictions in many films and paintings until the 1990s, when films such as Jurassic Park introduced a more accurate posture to the general public.

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5.Tyrannosaurus rex arms are tiny when compared to its overall body size, measuring only 1 metre long, and some scholars have labelled them as vestigial.

However, the bones show large areas for muscle attachment, indicating considerable strength.

This was recognized as early as 1906 by Osborn, who speculated that the forelimbs may have been used to grasp a mate during copulation.

It has also been suggested that the forelimbs were used to assist the animal in rising from a prone position. Another possibility is that the forelimbs held struggling prey while it was killed by the tyrannosaurs enormous jaws.

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6. Skin impressions from a specimen discovered in Montana show that in some part, the T rex has small patches of mosaic scales on its body.

However, other specimens show preserved feathers on various sections of the body, strongly suggesting that its whole body was covered in feathers. It is currently assumed that the extent and nature of feather covering in tyrannosaurids may have changed over time in response to body size, a warmer climate, or other factors.

To conclude

The debate about whether Tyrannosaurus was an active predator or a pure scavenger, however, is as old as the debate about how it stood and moved. Ever since the first discovery of Tyrannosaurus most scientists have speculated that it was a predator. Like our modern-day large predators it would readily scavenge or steal another predator's kill if it had the opportunity.

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Paleontologist Jack Horner has been a major advocate of the idea that Tyrannosaurus was exclusively a scavenger and did not engage in active hunting at all.

However, Horner himself has claimed that he never published this idea in the peer reviewed scientific literature and used it mainly as a tool to teach a popular audience, particularly children, the dangers of making assumptions in science (such as assuming T. rex was a hunter) without using evidence.

Nevertheless, Horner presented several arguments in the popular literature to support the pure scavenger hypothesis:

1. With regards to the Tyrannosaurs short arms, Horner argues that they were too short to make the necessary gripping force to hold onto prey.

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2. Tyrannosaurs had large olfactory bulbs and olfactory nerves (relative to their brain size). These suggest a highly developed sense of smell which could sniff out carcasses over great distances, as modern vultures do. Research on the olfactory bulbs of dinosaurs has shown that Tyrannosaurus had the most highly developed sense of smell of 21 sampled dinosaurs.

3. Tyrannosaur teeth could crush bone, and therefore could extract as much food (bone marrow) as possible from carcass remnants, usually the least nutritious parts. Karen Chin and colleagues have found bone fragments in coprolites (fossilized faeces) that they attribute to tyrannosaurs, but point out that a tyrannosaur teeth were not well adapted to systematically chewing bone like hyenas do to extract marrow.

Opposition

Opponents of the pure scavenger hypothesis have used the example of vultures in the opposite way, arguing that the scavenger hypothesis is implausible because the only modern pure scavengers are large gliding birds, which use their keen senses and energy-efficient gliding to cover vast areas economically.

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However, researchers from Glasgow concluded that an ecosystem as productive as the current Serengeti would provide sufficient carrion for a large theropod scavenger, although the theropod might have had to be cold-blooded in order to get more calories from carrion than it spent on foraging. They also suggested that modern ecosystems like Serengeti have no large terrestrial scavengers because gliding birds now do the job much more efficiently.

Other evidence suggests hunting behaviour in Tyrannosaurus. The eye-sockets of tyrannosaurs are positioned so that the eyes would point forward, giving them binocular vision slightly better than that of modern hawks. Horner also pointed out that the tyrannosaur lineage had a history of steadily improving binocular vision. It is not obvious why natural selection would have favoured this long-term trend if tyrannosaurs had been pure scavengers, which would not have needed the advanced depth perception that stereoscopic vision provides. In modern animals, binocular vision is found mainly in predators.

For related articles click onto the following links:
DINOSAUR: Archaeopteryx
DINOSAUR: Did Pterosaurs hang upside down?
DINOSAUR: The Pterodactyl
LIVING DINOSAURS - The Coelacanth
TERRA NOVA - Dinosaur trailer
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The Tyrannosaurus rex - http://animals.nationalgeographic.com/animals/prehistoric/tyrannosaurus-rex/