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Introduction

Triassic

Jurassic

Cretaceous

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The Cretaceous period takes its name from the Latin creta for chalk, which was deposited towards the latter half of the period. It is the last period of the Mesozoic era where we know that the first seed bearing plants developed and the dinosaurs reached their peak before they became extinct towards the end of the Cretaceous.

During the early Cretaceous the climate was sub tropical with wet and dry seasons but by the end of the Cretaceous the world began to look much more like we know it today.

A new type of dinosaur appeared called Ornithopods. The most famous were the Iguanodon, which was one of the first dinosaurs to be able to chew it’s food, and Ornithocheirus, which had wings 12m long and could fly up to 500 km’s.

In addition we see the development of bird like dinosaurs such as Velociraptor or Utahraptor and which had a deadly sickle claw making it a fierce fighter. Another well known theropod was Spinosaurus, a dinosaur with a distinctive sail on its back for regulating its body temperature.

Archaeopteryx is the earliest known bird which appeared towards the end of the Jurassic  / early Cretaceous periods. During the Cretaceous though the flying reptiles developed the largest being the Pterosaurs of which there were two types those with tails and those without.

The tailless Pterosaurs or Ornithocheirus took over from the tailed species and grew to great size. Although they looked clumsy on land they were extremely competent in the air where their 12m wing span allowed them to glide with ease. They looked like a cross between a bird and a bat with a long bird type beak but large bat like wings.

Evidence supports the existence of dinosaurs in the Polar Regions and the Dwarf Allosaur was the main predator in the Antarctic.

Towards the end of the Cretaceous (approx 65 million years ago) we see the appearance of perhaps the most famous and largest carnivore to walk the earth; Tyrannosaurus Rex a Theropod, it could eat 70kg of meat in one go.

It takes its name from the Greek ‘tyrannos’ or tyrant, ‘sauros’ or lizard and the Latin ‘rex’ for king. Less than 20 skeletons have been found all in the USA. It grew up to 12m long and up to 5.5m tall weighing over 6 tonnes. It had 60 teeth some of which were up to 30cm long.

The T. Rex could walk on its massive back legs while its front arms were shorter were to help counter balance the huge head.

Spinosaurus

EXTINCTION OF THE DINOSAURS

Towards the end of the Cretaceous Period about 65 million years ago the dinosaurs became extinct. The big question is WHY ?

This question has caused endless speculation amongst paleontologists. Over the years and there have been many theories put forward ranging from the probable to the downright ridiculous.

The two most probable theories are the Gradualistic and Catastrophic Theories none of which have been proven and neither fully explain why some types of animals survived yet others did not.

Gradualistic Theory

This theory is based on the theory of climate change over a period of time. It is known that the climate towards the end of the Cretaceous was cooling and there were numerous volcanic eruptions that could have caused severe environmental changes.

These climate / environment changes would then lead to the decline in the numbers and diversity of the dinosaurs eventually making them extinct.

Catastrophic Theory

This is the more spectacular theory. There is evidence that towards the end of the Cretaceous that there was an asteroid impact. The theory is that this would have been the catalyst for the earth’s eco system to change dramatically enough to wipe out the dinosaurs.