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Cretaceous Period Key Facts
Timescale: 144 million years ago to 65 MYA.
Environment: dispersing continents; tropical, sub-tropical, arid and temperate climates; cool polar conditions.
Notable dinosaurs: Tyrannosaurus rex, Velociraptor, Triceratops.
Other animals: mammals; flying reptiles (pterosaurs); birds; insects; marine life.

Cretaceous Period dinosaurs were many and varied. But they were also doomed. A mass extinction event at the close of this period spelled the end for dinosaurs. Before they bowed out, however, the dinosaurs gave us a truly memorable beast - Tyrannosaurus rex.

Familiar world?
During the early Cretaceous, there were two large continents, Gondwana to the south (comprising South America, Africa, peninsular India, Australia and Antarctica) and Laurasia to the north (comprising North America, Europe and Asia). By the end of the period, these vast landmasses had sub-divided and moved much closer to their present positions. Australia was still connected to Antarctica, though, and India had not yet joined Asia. Overall, it was one of the warmest times in Earth's history, except for the polar latitudes, where scientists believe temperatures dropped below 0 degrees Centigrade during winter.

Enter the king
If there's one dinosaur that everyone's heard of, it's Tyrannosaurus rex ("tyrant lizard king"). This terrifying predator evolved during the late Cretaceous and grew to 12 metres. It weighed around 5 tonnes and could open its massive jaws an eye-watering 1 metre wide. Those jaws, with their strong teeth, weren't just capable of ripping flesh. They could crunch through bone, too! But Tyrannosaurus wasn't all brute force. It had acute, binocular eyesight, ultra-sensitive hearing and a highly developed sense of smell that may have helped it locate dead animals it could scavenge, as well as live prey. Like Allosaurus from the Jurassic Period, it seems that Tyrannosaurus may also have looked after its young.

Killer speed merchant
Compared to Tyrannosaurus, Velociraptor ("quick plunderer") was a lightweight at just 1.8 metres and 7kg - 15kg. But what Velociraptor lacked in size it made up for in ferocity and killing efficiency. And speed. Velociraptor could reach speeds of 64kph, using its tail as a counterbalance on tight turns. In addition to a mouthful of razor-sharp teeth, Velociraptor had huge claws on its feet and hands. It used these to climb up larger prey. As if one Velociraptor on its own wasn't enough, these vicious late Cretaceous killers hunted in packs. And we all know how scary that can be from watching Jurassic Park...

Don't call me frilly
Triceratops ("three-horned face") is the most famous of the horned dinosaurs. This late Cretaceous animal grew to around 9 metres and weighed up to 10 tonnes. As well as three deadly horns, Triceratops had an impressive bony frill behind its head. Palaeontologists believe this was used in courtship and in ritual combat with rivals. Triceratops was a herbivore. Its jaws ended in a quasi-beak that would have helped it gather tough vegetation. Palaeontologists have established that many horned dinosaurs were herding animals but no Triceratops fossils have ever been found together. It seems that Triceratops was a bit of a loner.

Up, up and away
The skies above late Cretaceous dinosaurs were busy. Pterosaurs, huge flying reptiles with wingspans of up to 12 metres, had once been numerous but were on the decline during the late Cretaceous. Their place was being taken by direct descendents of dinosaurs - birds. Birds had evolved from the theropod group of dinosaurs, which included bipedal predators such as Velociraptor and Tyrannosaurus rex. By the late Cretaceous, birds were widespread in forests and mudflats. Some resembled modern birds, such as curlews and sandpipers. There was even a forerunner of today's parrot family.

The great extinction
We don't know what caused it but, at the end of the Cretaceous, there was large-scale extinction in marine and terrestrial life. Other life-forms, including reptiles and mammals, survived but dinosaurs - except for birds, of course - became extinct. Debate over the cause of this mass extinction is intense. Some scientists believe that an increase in volcanic activity, together with the effects of the shifting continents, caused profound climate change on Earth. Another theory is that a massive extraterrestrial object hit the planet, throwing up a huge dust cloud that obscured the sun, triggering climatic changes. Whatever the explanation, the age of the dinosaur was over.

Quick dino-facts

Traditionally, the arms of Tyrannosaurus were thought to be weak and useless. Now, palaeontologists believe there's evidence that these arms were strong, with nearly opposable fingers. No one's sure what T. rex used his strong little arms for, though!

Much of the evidence on the diet of dinosaurs comes from the study of their fossilised dung.

The Velociraptors in Jurassic Park were portrayed at twice their actual size.

Jurassic Period Key Facts
Timescale: 206 million years ago (MYA) to 144 MYA.
Environment: closely grouped continents; tropical, sub-tropical, temperate and arid climates.
Notable dinosaurs:Diplodocus, Brachiosaurus, Stegosaurus, Allosaurus.
Other animals: early mammals; flying reptiles (pterosaurs); early birds; insects; marine life.

There had been no holding back dinosaurs by the end of the Triassic Period. Then, during the Jurassic Period, they became the dominant animal life-form on the planet. Not only that, but Jurassic dinosaurs were big - very big. Giant herbivores, known as sauropods, evolved during the Jurassic. They were the largest land animals ever to walk the Earth.

An evolving world
Jurassic Earth was on the move. The Pangaea super-continent began to split into two during the mid-Triassic and this trend continued during the Jurassic Period. As early versions of today's continents moved away from each other, the oceans began to exert more influence on Earth's weather: the climate became far more varied. Vegetation was becoming more sophisticated, too. Palm-like plants and conifers flourished. Some experts also believe that the first flowering plants developed at the end of the Jurassic.

Land of the giants
The late Jurassic Period is renowned for huge dinosaur herbivores, known as sauropods. The largest grew to more than 40 metres in length and probably weighed up to 100 tonnes. You wouldn't have wanted one of these titans to step on your toe but sauropods weren't as heavy as their size might have suggested. They were actually quite lightly built creatures: much of their apparent bulk was due to internal, air-filled sacs.

Not walking in water
Palaeontologists used to believe that sauropods were amphibians. Artists' impressions of the large herbivores always depicted them grazing in lakes. It wasn't thought possible that sauropods could support their supposed vast weight without the buoyancy of water. Today's dinosaur experts are confident that sauropods had legs that were akin to a modern elephant's - easily able to support their own body weight.

Huge herder
Long-necked and long-tailed, Diplodocus ("double beam") is probably the best-known sauropod. Herds of these giant dinosaurs dominated the late Jurassic period. They were so big (25 metres and over) that they would have changed the landscape around them. To get at its food, diplodocus tore up saplings and pushed over trees, creating open plains. Everything about diplodocus was big - even its eggs were a hefty 25 centimetres across.

Tree grazer
Brachiosaurus ("arm lizard") was another well-known late Jurassic giant. Tall rather than long, brachiosaurus could grow up to 30 metres. It had a long neck that allowed it to graze among treetops and long legs that kept its body high off the ground. Its front shoulders were higher than its haunches, giving it a sloped appearance rather like a modern giraffe.

Stegosaurus ("roof lizard") was a medium-sized herbivore of the late Jurassic. Around 7 metres long and up to 3 tonnes in weight, Stegosaurus had a series of large, bony plates running along its spine. Experts have suggested several uses for these plates. They could have been used in courtship display or they may have served as heat-regulating devices. Perhaps they were defensive armour or maybe Stegosaurus could have made itself more terrifying in combat by pumping the plates with blood. At any rate, Stegosaurus was no pushover in the dangerous world of Jurassic Earth. It had a fearsome defensive weapon - a powerful, spiked tail that could deliver crippling blows to would-be predators.

Jurassic slasher
As large herbivores became more prevalent, bigger predators emerged, too. Allosaurus ("other lizard") was the commonest large predator of the period. Around 12 metres long, it is known to have preyed on big sauropods as well as smaller animals. Its curved teeth and huge jaws inflicted deep slashing wounds on its victims. You wouldn't last long once you were corned by an Allosaurus. Nimble prey might have outrun this predator, though, because it wasn't capable of sustained bouts of speed. Interestingly, there is some evidence that Allosaurus cared for its young, bringing back meat for its offspring, who lived in a protected den until they were old enough to fend for themselves.

Quick dino-facts

Three stars of Jurassic Park - Triceratops, Tyrannosaurus rex and Velociraptor - weren't actually around during the Jurassic Period. They didn't evolve until the late Cretaceous.

After studying fossil tracks, modern palaeontologists concluded that giant sauropods walked with their tails held aloft, not dragging along the ground.

Giant sauropods had large stones in their stomachs to help them digest tough vegetation.

Triassic Period Key Facts
Timescale: 248 million years ago (MYA) to 206 MYA.
Environment: one continent (Pangaea), that began to break up; hot, semi-arid, seasonal rainfall.
Notable dinosaurs: Coelophysis, Plateosaurus.
Other animals: crocodile-like terrestrial predators; beaked herbivores; flying reptiles (pterosaurs); proto-mammals; insects; marine life.

The Triassic Period was the first period of the Mesozoic Era, which ran from 248 million years ago (MYA) to 65 MYA. A lot happened to Earth and its life-forms during the Triassic but the most celebrated event was the evolution of dinosaurs. These remarkable creatures emerged around 230 MYA and dominated the planet until the end of the Mesozoic Era.

One world, one continent
Planet Earth looked very different at the beginning of the Triassic Period. There was just one landmass, a huge continent known as Pangaea. It stretched from pole to pole and included a vast desert at its centre. There was no grass, ...

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