Dinosaurs
Dinosaurs are a group of reptiles that dominated the land for over 140 million years. They evolved into diverse shapes and sizes. The word 'dinosaur' means 'terrible lizard', and comes from the Greek words 'dino' meaning terrible and 'saur' meaning lizard.
One of the reasons for dinosaurs' success is that they had straight back legs. This allowed them to use less energy to move than other reptiles that had a sprawling stance, like todays lizards and crocodiles. This also meant dinosaurs' wheight was also better supported.
Many dinosaurs species became extinct around 66 million years ago, but a group of living dinosaurs are still with us today; birds.
Archaeopteryx
Archaeopteryx is the earliest known bird. All birds are dinosaurs, they belong to the same group as small, two-legged dinosaurs such as Velociraptor and Compsognathus.
Phalacrocorax auritus
The double-crested cormorant is a member of the cormorant family of water birds. Its habitat is near rivers and lakes as well as in coastal areas, and is widely distributed across North America, from the Aleutian Islands in Alaska down to Florida and Mexico.
Prehistoric History
Dinosaurs are archosaurs, a larger group of reptiles that first appeared about 251 million years ago, near the start of the Triassic period.
Some other reptiles are also archosaurs, such as: crocodiles and their ancestors.
When did dinosaurs live?
Non-bird dinosaurs lived between ~245 and 66 million years ago, in a time known as the Mesozoic Era. This was many millions of years before the first modern humans appeared.
Scientists divide the mesozoic era into three periods: The Triassic, Jurassic and Cretaceous. Durning this period the land gradually split from one huge continent into smaller ones. The associated changes in the climate and vegetation affected how dinosaurs evolved.
Triassic Period (252-201 million years ago)
Land= Pangea (single land mass)
Climate= Hot & dry, lots of deserts with no polar ice caps.
In this period dinosaurs first evolved. Reptiles tend to flourish in hot climates because their skin is less porous, so it loses less water in the heat. Reptiles kidneys are also better at conserving water.
Toward the end of the Triassic Period there was a series of earthquakes and massive volcanic eruptions causing Pangaea to slowly break in two. This was the birth of the North Atlantic Ocean.
Jurassic Period (201-145 million years ago)
Land= 2 parts Laurasia (North) and Gondwana (South)
Climate= Lower temperature and increased rain fall due to large seas.
At the end of the Triassic Period there was a mass extinction. Many animals were wiped out but dinosaurs survived and they evolved, increasing their variety and number.
Cretaceous Period (145-66 million years ago)
Land= Further split into some of the continents as we know them today.
Climate= Sea levels rise and land diversified.
The first snakes evolved durning this time as well as the first flowering plants. Various insect groups also appeared, including: bees; which helped increase the spread of flowering plants. Mammals now included tree climbers, ground dwellers and even predators of small dinosaurs.
Did you know...
Due to the increase in sea levels thick layers of sediment built up at the bottom of the sea bed as single-celled algae died and their skeletons fell to the sea bed. this is how most of the chalk we used today formed. So much that 'cretaceous' comes from the Latin for chalk, 'creta'.
Why did dinosaurs go extinct?
The end of the Cretaceous Period saw one of the most dramatic mass extinctions Earth has ever seen. The exact nature of this catastrophic event is still open to scientific debate. Evidence suggests an asteroid impact was the main culprit. Volcanic eruptions that caused large-scale climate change may also have been involved, together with more gradual changes to Earth's climate that happened over millions of years.
Did you know...
As a group, sharks have been around for at least 420 million years, meaning they have survived four of the “big five” mass extinctions. That makes them older than humanity, older than Mount Everest, older than dinosaurs, older even than trees.
Dinosaur Species
There are many diverse dinosaur species, from slow plant eating to firece scavengers and hunters, that once dominated the land.
Top Five Dinosaurs
Triceratops
Plant eater with specialised teeth for cutting and slicing. It's huge stomach could digest tough plant matter. It's horn would be used to defend itself.
Stegosaurus
Slow moving plant-eater with spices on it's tail to fend of predators. The spiny plates on it's backs use is still unknown however it is generally usually considered that the may have been used primarily for display, and for thermoregulatory functions.
Tyrannosaurus
Meat eating predator. Lived in the creteaous period.
Diplodocus
Plant eating, long neck dinosaur. It's teeth were in rows like a comb.
Coelophysis
Small meat-eater, was one of the earliest dinosaurs. It was fast and algail and eats small reptiles and insects.
Types of Dinosaur
Armoured= Medium-sized, four legged herbivores with body armour, sometimes including tail spikes.
Ceratopsians= Herbivores with parrot-like beaks, bony frills and in many cases horns.
Euornithopods= Medium-sized herbivores that usually walked on two legs.
Sauropods= Very large herbivores that walked mostly on four legs.
Large Theropod= Large carnivores that walked on two legs.
Small Theropod= Large Carnivores, herbivores and omnivores that walked on two legs and often had feathers. Birds are part of this group.