Spinosaurus was one of the most spectacular-looking dinosaurs of all time. It was a huge, meat-eating creature that was prabably a very succesful predator because of the special adaptations to its body. The most noticeable thing about Spinosaurus was the amazing "sail" that stuck out of its back. this sail was made up of spike-shaped spines of bone that stuck up from its backbone, joined together by a layer of skin.

Discovery

As fossils, the giant spines look almost like giant thorns, which is how Spinosaurus got the name "thorn lizard" when it was discovered by a dinosaur hunter named Stromer in 1951. The sail of a fully grown male Spinosaurus would have been well over 2 metres ( 6 feet ) long, which is taller than a big man. And that's just the sail-the rest of the dinosaur measured 12 meatres ( 40 feet )! Such a heavy body part must have had an important job.

The weight of this huge structure means that Spinosaurus is one of the heaviest meat-eating dinosaurs ever. It weighed just a little less than Tyrannosaurus, the largest meat-eater to live on planet Earth at any time.

Body Facts

Powerful jaws held teeth that were straight, rather than curved like most other meat-eating dinosaurs. Having longer arms than most other two-legged meat-eaters suggests that Spinosaurus may have spent some time walking on all fours. Its spines were up to 2 metres (6.5 feet) long, projecting from the backbone. The skin of Spinosaurus' s sail may have been brightly coloured for display, as a way of attracting females. The spines were linked by a layer of skin, which probably carried many blood vessels and helped Spinosaurus warm up.

What was the sail for?

There are lots of theories about the uses of Spinosaurus's sail. The most popular is that it was used to control the dinosaur's body temprature. Early in the morning Spinosaurus would have turned its sail towards the sun, which would have warmed the blood as it passed through the sail. This is part of the reason for Spinosaurus being such a great hunter: because it warmed up more quickly than the cold - blooded reptiles on which it fed, it was faster moving than they were in the morning . Spinosaurus must have eaten lunch early every day!

Another theory is that Spinosaurus's sail could have been brightly coloured. As well as being used to control its body temprature, it would have been used by males to attract females, in the same way as peacocks use their fans. The males might also have used their sails to compeate with each other when trying to decide which of them was the toughest dinosaur in the neighbourhood.

EUROPEAN RELATIVES

A new African dinosaur from the same family as Spinosaurus , called Suchomimus, has been discovered . It has a long snout like a crocodile, which is very similar to that of the European dinosaur Baryonyx. Perhaps Spinosaurus had distant relatives living in Europe.

Fast Facts

Edmontosaurus was a large, duck-billed herbivore that probably lived in herds, with others of its kind. It walked on two legs, but when feeding on low-growing plants it probably moved slowly on all fours. Its beak nipped and tugged at flowering plants and the tough leaves of conifer trees. Edmontosaurus ate bark and pine-cones, too. Once inside its mouth, its tongue pushed food into the cheek pouches that lay along either side of its jaw. Rows of tiny inter-locking teeth then began to chew on the food, grinding it down until it was ready to swallow.

Discovery

Edmontosaurus lived at the very end of the Age of Dinosaurs, in parts of western Canada, and the USA. It is named after Edmonton, Canada, near where many of its fossils were originally found. At first this dinosaur was called "Caloasurus", and for many years museums used this name when they put specimens on display. But in 1917, the palaeontologist, Lawrance Lambe, studied this duck-billed creature in greater detail than anyone had before, and as a result it was renamed Edmontosaurus. Edmontosaurus heards may have migrated, or travelled, over thousands of miles every year, since large numbers of their skeletons have been found in two seperate places - one in Alaska, the other in Alberta, Canada. Perhaps the animals followed a trail between these places that led them to food at different seasons of the year.

Body Facts

Edmontosaurus had a long, pointed tail. Each foot had three toes. It had short arms. Its head had a broad snout, like a duck's bill, long jaws with cheek pouches and large eyes. At the tip of its snout was a horny beak-like covering. There were as many as 1,000 tiny teeth - called a dental battery - set towards the back of its jaws. They could be locked together in a grinding pattern. Asw old teeth fell out, new ones grew in their place. It had large nostrils, covered with folds of skin.

Dinosaur Mummy

In 1908, Charles Sternberg and his three sons made one of the most incredible of all dinosaur discoveries - a 65-million-year-old mummified Edmontosaurus. They were searching for bones in the Lance Creek area of Wyoming, USA, when they came across the remains of a Edmontosaurus lying on its back. As they uncovered the creature the shrunken remains of its fossilized skin were found, still streched over the animal's body. It was an unbilievable find.

NOISY NOSE

Because the nostrils of Edmontosaurus were large and hollow, palaeontologist wonder if its nose was covered in folds of loose skin. When it inflated these folds, by blowing air though its nostrils, the effect might have been to create a "sound chamber", which made loud, bellowing

Albertosaurus comes from the same dinosaur family as a better known and slightly larger relative, Tyrannosaurus. It lived before Tyrannosaurus, and the two creatures are similar in several ways - both had large heads and tiny front arms. A noticeable difference between Albertosaurus and its close cousin Tyrannosaurus is in the position of its eyes. While the eyes of Tyrannosaurus looked straight ahead, those of Albertosaurus were positioned at the sides of its head. As a meat eater, or carnivore, Albertosaurus was a hunter. It was a "land shark" that preyed on slower-moving animals, such as duck-billed dinosaurus the size of modern rhinoceroses. Their only chance of escape from the kicks and blows of its powerful legs would have been to out run it, or drive into thick vegetation for cover. In Canada, a group of Albertosaurus skeletons have been found close together in one place, and this suggested it lived in packs with its fellow dinosaurs.

Discovery

In 1884 Joseph Tyrrell Led an expedition from the Canadian Geological Survey to explore part of Alberta, a vast area in the west of Canada. Has team of scientists set out to make the first detailed maps of the region and to look for useful mineral deposits. But, as well as discovering vast deposits of coal, they found something totally unexpected. On June 9, in the valley of the Red Deer River, Tyrrell discoverd fossilized bones belonging to a large meat-eating dinosaur. Although these were not the first dinosaur remains found in Canada (the first were found in 1874), they caused great excitment because they came from a preveously unknown speicies. The new dinosaur was named Albertosaurus after the area in which it was found. Many other Albertosaurus fossils have since been found in Alberta, Canada and in the western USA.

Body Facts

Its body was balanced by a long, flexible tail. Albertosaurus walked on two strong, muscular back legs. It was probably a fast runner - up to 30 kph (19 mph). Its tiny front arms ended in two small fingers. Like Tyrannosaurus, Albertosaurus had a large head. Two small, blunt horns near its eyes may have been used for display - to attack a mate or frighten an enemy. The eyes of Albertosaurus were on the sides of its head. because of this, it is thought that Albertosaurus could not see as well as Tyrannosaurus. Dispite its poorer eyesight, Albertosaurus was still a firce predator.

THE MOST COMPLETE CARNIVORE

The Albertosaurus specimen on display in the American Museum of Natural History, New York, is one of the most complete fossils of a meat-eating dinosaur found in North America. It was discovered in 1917 by the fossil collector, Charles Sternberg, and bought by the Museum in 1918 for US $ 200

Siberian (or Amur) tigers are the world's largest cats. They live primarily in eastern Russia's birch forests, though some exist in China and North Korea. There are an estimated 400 to 500 Siberian tigers living in the wild, and recent studies suggest that these numbers are stable. Though their northern climate is far harsher than those of other tigers, these animals have some advantages. Northern forests offer the lowest human density of any tiger habitat, and the most complete ecosystem. The vast woodlands also allow tigers far more room to roam, as Russia's timber industry is currently less extensive than that of many other countries.

Tigers are the largest of all wild cats and are renowned for their power and strength. There were once eight tiger subspecies, but three became extinct during the 20th century. Over the last hundred years, hunting and forest destruction have reduced overall tiger populations from hundreds of thousands to perhaps 5,000 to 7,000. Tigers are hunted as trophies and also for body parts that are used in traditional Chinese medicine. All five remaining tiger subspecies are endangered, and many protection programs are in place. Poaching is a reduced—but still very significant—threat to Siberian tigers.

Tigers live alone and aggressively scent-mark large territories to keep their rivals away. They are powerful hunters that travel many miles to find prey, such as elk and wild boar, on nocturnal hunts. Tigers use their distinctive coats as camouflage (no two have exactly the same stripes) and hunt by stealth. They lie in wait and creep close enough to attack their victims with a quick spring and a fatal pounce. A hungry tiger can eat as much as 60 pounds (27 kilograms) in one night, though they usually eat less.

Despite their fearsome reputation, most tigers avoid humans; however, a few do become dangerous maneaters. These animals are often sick and unable to hunt normally, or live in areas where their traditional prey has vanished.

Females give birth to litters of two to six cubs, which they raise with little or no help from the male. Cubs cannot hunt until they are 18 months old, and remain with their mothers for two to three years, when they disperse to find their own territory.