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| Sunday, 9 October 2005 |
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Junior Observer |  |
| News Business Features Editorial
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When dinosaurs ruled the world : T-rex and two-legged hunters
Theropods or the meat-eating dinosaurs were also called carnosaurs. Among the early carnosaurs none was more terrible than Allosaurus which means 'leaping lizard'. It was about 12 metres long, had short front legs and two huge hind legs which was armed with sharp claws. It had a thick neck which supported a large head with mighty jaws, that were bristling(covered) with knife-like teeth. Allosaurus was a deadly two-legged hunter that preyed upon the sauropods of North America about 150 million years ago. The largest and the most terrifying of the carnosaurs was however the Tyrannosaurs or the 'King tyrant lizard' that lived about 70 million years ago. The best known among these is Tyrannosaurs rex. At around 12-14 metres long, with thick, powerful hind legs that had claws like carving knives, and sharp teeth, it was one of the largest and deadliest creatures that has ever lived on land.
The T-rex as it's popularly known today, strangely had very small front legs or arms and hands for an animal of such power. They were too small to be used as weapons, and in fact too short even to bring food to its mouth which contained, strong and deadly teeth. In fact, its teeth were about 18 centimetres long with razor-sharp points to stab the prey, and rough, saw-like edges to rip through the flesh. An adult had between 50 to 100 teeth and if one fell out, it simply grew another! It is rarely that complete fossil skeletons are found, but in 1990 two almost complete Tyrannosaurs skeletons were found in America and experts studying these and other Tyrannosaurs skeletons believe that unlike meat-eaters of today, such as the lion and the tiger, the female Tyrannosaurs was probably bigger and stronger than the male. Dilophosaurus, Allosaurus and Albertosaurus are three meat-eaters related to Tyrannosaurs, but they were not as big. Two huge 2.6 metre long fossil arms with clawed hands found in Mongolia have been named Deinocheirus ('terrible hand') because experts believe they may be from a version of Deinonychus ('terrible claw') which was even bigger than Tyrannosaurs.
Experts used to think that Tyrannosaurs stood upright and lumbered along, with its tail dragging on the ground, but by studying the more complete skeletons, they are now of the view it leaned forward, with its tail sticking out as a balance. They also believe that it could run fast. Judging from the skull and the size of its brain, they think that it had good eyesight, hearing and an excellent sense of smell. Some experts are of the view that the T-rex could run as fast as a racehorse (50 kilometres an hour) and was a fierce hunter. They also say that Tyrannosaurs was a scavenger that ate dead animals and also stole prey from other predators.
Attack and defence methods As we are aware, all meat-eating dinosaurs were built to kill, with not only sharp teeth, but also powerful, slashing claws. So, how did the sauropods or plant-eating dinosaurs protect themselves from these killer machines? They did so in different ways. While some kinds of sauropods lived in herds to protect themselves, others depended on speed to escape the theropods. Some even developed armour and horns to fight their enemies. Huge sauropods such as the Diplodocus, used their long, whip-like tails to frighten off attackers, and plant-eating ankylosaurs ('rounded reptiles') protected themselves with armour-like skin and bony spikes.
They were long, low creatures with bony plates, spikes or knobs, protecting most part of the open to attack. The size of a tank, an Ankylosaurus if attacked had to crouch to protect its soft belly. Its defence weapon was the bony club at the end of its tail which it used to lash out at its enemies. The two kinds of early anklyosaurs that roamed southern England were Acanthopholis, a beast about four metres long with flat bony plates and Polacanthus which depended on spikes for its defence. Only the an ankylosaur's belly was soft and vulnerable, but few beasts could overturn long plated giants. Stegosaurs on the other hand was well protected from its enemies with huge bony plates along its back and four long, sharp spikes on its thick tail. A blow from its tail was enough to kill or seriously injure an attacker. The plates along the back of Stegosaurs were covered with skin and had lots of blood vessels in them. Some experts are of the view that they may have helped the dinosaur warm its body when sun-bathing. The North American dinosaur 'Euoplocephalus was considered a monster because though it was only half as long as Stegosaurs, it was twice as heavy. Scolosaurus was another armoured dino which was hard to attack.
The ankylosaurs lived until the Age of the Dinosaurs ended because they could fight and protect themselves better than most other dinosaurs. But there were more powerful dinos with formidable horns. When cannosaurs attacked the armoured dinosaurs, most of them just stood, cranked or swished their heavy tails, but the horned dinos used their strong horns which sprouted from their heads somewhat like those of the present day rhinoceros. Next week Horned dinos and more.... |
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