The word DINOSAUR means terrible lizard.
Although there were several different sorts of creature in existence in prehistoric times, not all of these creatures were dinosaurs. Dinosaurs were the reptiles of the land. Dinosaurs walked on two or four legs, they could not fly or swim. The prehistoric creatures that flew or swam were other sorts of reptiles. The flying reptiles are pterosaurs. The water-based reptiles are ichthyosaurs or plesiosaurs. Plesiosaurs are very big, long-necked reptiles with flippers instead of legs. Ichthyosaurs are smaller, dolphin-like reptiles with sharp teeth. There were also other land-based reptiles that were not dinosaurs living at the same time, for example, the mammalian reptile Dimetrodon.
These creatures are not dinosaurs:
ICHTHYOSAURUS a sea reptile (ichthyosaur)
BATRACHOGNATHUS a flying reptile (a small pterosaur)
DIMETRODON a mammalian reptile
All the creatures above lived at the time of the dinosaurs, but they were not dinosaurs, just reptiles.
Here is a profile on a non dinosaur:
Its name means water lizard
It weighed 3-4 tons
It ate fish and other water creatures
It lived in what is now the Atlantic ocean and the North sea
It was 6m long
It had a neck with 72 vertebrae
The periods that DINOSAURS lived in (in order) were the:
Triassic 245-200 million years ago (First dinosaurs evolve)
Jurassic 200-135 million years ago (Pangaea breaks into continents)
Cretaceous 135-65 million years ago (Dinosaurs became extinct 65 m.y.a)
Tertiary 65-1.8 million years ago (First large mammals appear)
All dinosaurs were in existence from 235 million years ago to 65 m.y.a. when they became extinct.
The ancestors of dinosaurs lived in the CARBONIFEROUS period 350 m.y.a. By the Cretaceous period (115 Million years later) they had evolved into the strange, terrible lizards. But before we reach them there are some other prehistoric creatures to read about.
The Triassic Period
At the beginning of the time of the dinosaurs they were not the giants people think they were. During the Triassic period the biggest dinosaurs were only about 1 meter tall! The first mammals appeared in the middle of the Triassic period, 217 million years ago. These mammals were no bigger than large rats. One sort Megazostrodon, a species of prehistoric mammal was no bigger than a hamster, it ate small insects. The super-continent Pangaea starts to break up.
Some of the differences you might notice about the landscape are:
that there is no grass in the Triassic Period,
that there are no forests in the Triassic Period.
THE JURASSIC PERIOD
During the Jurassic period the sea rises and the land drifts further apart. Dinosaurs evolve into different species that can only be found in one or two places. The Jurassic also saw the arrival of birds, even though birds now existed, the skies were still ruled by Pterosaurs (flying reptiles).
Here is a profile on a pterosaur:
It had wings made of membrane.
It walked on four legs.
It weighed about 10 k.g.
It ate fish.
It lived in Europe.
It distinguishing feature was its dinosaur like head.
In the top picture there is a running dimorphadon, on its hind legs which are made of cartilage. In the bottom picture is a dimorphadon skeleton.
Two of the things you might notice about the Jurassic period are:
not many open spaces (plains).
The Cretaceous Period
During the Cretaceous period the famous dinosaurs appeared, like Tyrannosaurus Rex, and Triceratops. In this period the world was almost as it is today except for the positions of the continental plates which are not quite in the positions they are in now. The world was beginning to look like it does today.
Here are some profiles of a few of the dinosaurs alive at this time:
Its name means giant duck.
It was mostly bipedal.
It weighed 3 tons.
It was a herbivore.
It lived in North America.
It stood out from other dinosaurs because of its beak.
Its name means king of the tyrant lizards
Weighed 6 tons.
Scavenger of meat
Lived in North America, China and India.
It is 6m tall.
Its name means similar to crested reptile.
It was both bipedal and quadruped.
Its weight is unknown.
Lived in North America.
It had a crest/horn on the back of its head.
Here are two pictures of parasaurolophus showing it on two legs (biped) and four legs (quadraped).
At the end of the Cretaceous period dinosaurs became extinct.
Here some reasons people thought dinosaurs became extinct are:
Sudden climate change.
New poisonous plants.
I think that the meteor did not directly cause the extinction, because
about 65 m.y.a the earth's axis moved slightly away from the sun. I think
that the meteor hit earth and changed the earth's axis and moved the earth
slightly away from the sun. What do you think?
But whatever reason, we know that the dinosaurs died out 65 M.Y.A.
After the Cretaceous came the Tertiary period, in this period pigs were the size of elephants. Horse like creatures appeared for the first time. Whales were in the seas with massive fish.
After the Tertiary period came the ice age were the world took its present form, and during the ice age the most efficient of all predators evolved: humans.
I hope from reading this you have learnt a few things.
I have learnt that you need to look at different sources. I have used the internet and books and CD roms to pull this project together. I found out about the creatures and time periods from books and CD roms. To get pictures I had to scour the internet.
Here are the abbreviations used:
M.Y.A.- million years ago
Compton's Interactive World Atlas Softkey Multimedia 1997
Dougal Dixon, Dinosaurs and other Prehistoric Animals Kingfisher 1998
Dinosaur Fact File Colliers 1994
Dr David Urwin The New Book Of Dinosaurs 1997
Oxford Interactive Encyclopedia Oxford University Press 1997
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