DINOSAURSFOR 150 MILLION YEARS, from the Triassic Period until the end of the Cretaceous Period, 65 million years ago, dinosaurs lived on Earth. Their remains have been discovered in every continent including Antarctica. They formed a varied group of land living reptiles. People who study prehistoric life, called palaeontologists, divide them into two main groups the Ornithischia and the Saurischia. There were meat-eating and plant-eating dinosaurs. Some dinosaurs, were huge; others were only the size of chickens.
IguanodonThis was one of the first dinosaurs to be discovered. Modern reconstructions give it an outstretched tail and forelimbs that can reach the ground.
Iguanodon skull : Gideon Mantell, an English doctor, named Iguanodon in 1825, noting the similarity between its teeth and those of the modern iguana. Iguanodon teeth were shaped to fit tightly together. They wore down as the dinosaur chewed its food of tough vegetation with the help of a hinged jaw.
Iguanodon foot : The feet of Iguanodon had small hooves on the toes instead of claws, and would have made recognizable three-toed prints with rounded digits. Iguanodon probably walked on its toes, which, therefore, had to be strong to carry the animals great weight.
Iguanodon spike : When Iguanodon was first reconstructed, its large spike was placed on its beak. It is now known that the spike was on its thumb and may have been used as a defensive weapon against predators. The spike could have pierced the belly, throat, or eye of an attacker. The dinosaur may also have used it in fights for status with other Iguanodon.
OrnithischiansThe Ornithischia, or bird hipped dinosaurs, such as Iguanodon, were all herbivorous. They had a huge number of teeth – Corythosaurus had 2,000 – and a hinged upper jaw that allowed them to chew.
TyrannosaurusAlthough not thought to be the largest of the carnivorous dinosaurs, Tyrannosaurus was still an extremely fearsome predator. It walked on its hind legs with its back level and head raised. It could run very fast, its tail balancing the weight of its huge heavy body.
Tyrannosaurus skeletonTyrannosaurus may have hunted as well as scavenged on other dinosaurs. It had a massive skull with powerful jaws, supported by a short flexible neck. This flexibility allowed the animal to twist it head around to wrench flesh from its prey.
Tyrannosaurus tooth : Carnivorous dinosaurs had curved, pointed teeth. The sharp edges often had serrations, which helped the dinosaurs to slice through skin and meat Palaeontologists still have to be careful when handling these teeth.
SaurischiansThe Saurischia, or lizard-hipped dinosaurs, include the meat-eating theropods, which walked on two legs, such as Tyrannosaurus, and the plant-eating sauropods, which walked on four legs, such as Diplodocus. The sauropods were the largest ever land animals.
HipsDinosaurs fall into one of the two main groups, according to the structure of their hip bones. The bird-hipped dinosaurs (ornithischians), such as Parasaurolophus, had a pubis bone in their hip girdle that sloped backward, parallel to the ischium bone. The lizard hipped dinosaurs (saurischians), such as Gallimimus, had a pubis bone that sloped forward away from the ischium.
Fossil dung : Preserved pieces of dung are called coprolites. They contain the remains of what dinosaurs ate, such as bone fragments, fish scales, or plant remains. Scientists can study these to find out about the diet of dinosaurs.
The first dinosaurs : One of the earliest dinosaurs was Eoraptor, meaning “early plunderer”. It was no bigger than a large dog and lived 225 million years ago (mya). As with all the early dinosaurs, it was a carnivore and walked on two legs.
BreedingDinosaurs laid hard-shelled eggs as some reptiles do today. Many dinosaurs laid a clutch of eggs in a hollowed-out nest in the ground. Several fossilized nests have been found close together, which suggests that some dinosaurs nested in colonies. The chicks developed rapidly and may have left the nest soon after hatching. Many were cared for by the parent dinosaur until they were able to look after themselves.
Richard Owen : Born in Lancaster, England, Richard Owen (1804-92) became the Hunterian Professor of the Royal College of Surgeons in 1836. As well as being an anatomist, he was a brilliant palaeontologist. He was the first to use the term “dinosaurs”, which means “terrible lizards”, in a report in 1842. He noted that these animals had pillar-like legs.
DefenceDinosaurs protected themselves against attack from predators. Different dinosaurs developed a variety of powerful defence. For example, Triceratops had horns on its head, Euoplocephalus had a tail club, and Tuojiangosaurus had a spiky tail. Some of these adaptations may have had several functions, but one of them was likely to have been defence. Scientists cannot say exactly how these animals defended themselves, but it is easy to imagine.
TuojiangosaurusThe flani and belly of T u r were vulnerable to attack Near the tip of is cal were four bony spikes. These pointed up and outwards, producing a formidable defence when the dinosaur swing its tail. This animal was a type of bird-hipped dinosaur called a stegosaurus. It lived in China 157-145 mya.
Dinosaur skin : Occasionally, the skin, or skin impression, of dinosaurs is preserved. From these fossils we can tell that the skin of many dinosaurs was not smooth, but nodular and rough. This would have given some protection against the claws and teeth of predators. This is the skin of Polacanthus.