geological time periods

Geological Time Periods

The time periods are very important to a palaeontologist.
The table below is a very simple Geological Time Line.
Click on the time period you wish to invisigate.

Tertiary Period

Tertiary fossil crabThis Era started 65 million years ago and finished 2 million years ago.
This Era is split into 5 parts.This was the Era of mammals.
Life in the Tertiary Era On land, the age of the mammals was beginning. Rodents evolved, as well as gliding mammals and the early primates. Sharks and fish took over from marine reptiles. Towards the middle of this Era, the ancestors of elephants, horses, cattle, pigs, rhinos and deer appeared. Other mammals such as whales and sea cows took to the water. Other groups of animals were also evolving, including ants and bees, starlings and penguins, moles, camels, cats, dogs and bears. Towards the end of this period , grazing hoofed animals spread and diversified. The ancestors of humans appeared in Africa.

Plant life in the Tertiary Era
In the early parts of this era, flowering plants continued to spread and diversify. Towards the end of this era the climate cooled, grasslands took over from the forest

Cretaceous Period

Cretaceous fossilStarted 144 million years ago and lasted to 65 million years ago. This was the period of the explosion of flowers.
The explosion of flowers Up until the beginning of the Cretaceous Period, the distribution of spores and pollen was a risky business. In the Cretaceous Period new and more effective ways of spreading pollen developed. Flowering plants were now evolving with a partnership with the insects.

Life in the Cretaceous Period
Giant turtles and marine reptiles dominated the oceans. On land snakes evolved. There were new kind of dinosaurs. Insects such as moths and butterflies, got there food from the new flowers. At the end of the period, there was a mass extinction which saw ammonites, ichthyosaurs, and many other marine groups to disappear and the dinosaurs became extinct.
Plant life in the Cretaceous Period
The following plants appeared and evolved relationships with insects for pollination. The flowers spread rapidly over the land.

Jurassic Period

Jurassic fossilThe Jurassic period started 213 million years ago and lasted until 240 million years ago. This was the first period to have birds.
Life in the Jurassic Period Turtles and crocodiles increased in numbers and variety. New species of plesiosaur and ichthyosaur arose. On land insects were thriving including ancestors of modern ants, bees, earwigs, flies and wasps. The first bird appeared. Dinosaurs ruled the land.

Plant Life in the Jurassic Period
Plants spread across the land as the climate became wetter. The of the modern cypresses, pines and redwoods appeared in the forests.

Triassic Period

This period started 248 million years ago and finished 213 million years. This period was the beginning of the Mesozoic era.
Life in the Triassic Period Dinosaurs and other reptiles became the dominate land animals. Frogs appeared and later the first tortoises, turtles and crocodiles. The first mammals appeared.

Plant Life in the Triassic Period
The cone-bearing plants diversified forming forests of cycads, monkey-puzzle trees, ginkgoes and conifers.

Permian Period

Permian fossil footprints

This period started 286 million years ago and went to 248 million years ago. This period was the period which reptiles took over.

Life in the Permian Period

Ammonities were still very abundant. Modern corals began to take over the early reefs. In the early part of this period amphibians dominated fresh water. Aquatic reptiles evolved. Towards the end of this period over 50% of the animal families disappeared, including many amphibians, ammonities and trilobites. Reptiles took over from amphibians on land.

Plant Life in the Permian Period

Conifers appeared and spread inland and up mountains. The southern land mass was dominated by forests of large seeding ferns.

Carboniferous Period

This period went from 360 million years ago to 286 million years ago. During this period insects were everyware and the decaying trees during this time produced the coal known today

Life in the Carboniferous Period
Ammonites and Brachiopods became more abundant. The age of amphibians appeared. Insects including grasshoppers, cockroaches, silverfish, termites, beatles and giant dragonflies also evolved. In the late part of this period the first reptiles appeared.
Plant Life in the Carboniferous Period
Dence forests of giant clubmosses, horsetails, tree ferns and sead plants up to 45m tall. The undecomposed remains of these forests develop into coal.

Devonian Period

The Devonian period started at about 410 million years ago and ended about 375 million years ago. This period was the age of the fish.

Life in the Devonian Period
During this period there was a rapid evolution of fish, including sharks and rays, lobe finned fish and ray finned fish. Ammonities increased in population. Giant squid up to two meters long hunted the seas. Many arthropods including spiders and wingless insects invaded the land.
Plant Life in the Devonian Period
Plants spread from the margins of the water to cover large areas of land in dense forest. Some trees developing up to 38m high.

Silurianan/ordovician Periods

Ordovician fossil

Silurian fossil

These time periods from 500 million years ago to 435 million years ago. In these periods powerful predators and reefs began to be built.

Life in the Ordovician and Siluran Periods

In these periods there was a great increase in filter feading animals. These included sea mats, sea lilies, brachiopods, molluscs and graptolites which all met their peak in the Ordovician period. Durying the Siluran period rugose corals were very active reef builders. This was the age of the great preditors including sea scorpions, and the first jawed fish. Brachiopods and trilobites thrived.

Plant life in the Ordovician and Siluran Periods

The first true plants first apeared in the late Ordovician period. In the Siluran period plant life surounded the margins around the water.

Cambrian Period

Cambrian fossil

The Cambrian period began about 570 million years ago. It lasted for about 70 million years. The period began with an astonishing explosion of evolution, during which most of the major groups of animals we know today made their first appearances on Earth.

The Cambrian Explosion

The Cambrian explosion is one of the biggest mysteries in the history of life. It took 2.5 billion years for simple cells to become more complex cells. It took another 700 million years for multicellular creatures to appear. Then, in just 100 million years, came a tremendous variety of multicellular animals. For over 500 million years not a single new basic body plan was evolved.

The Cambrian period sea level rose and fell making some populations extinct. As the Cambrian period went on, animals evolved new and more specialized ways of feeding thus creating a greater variety of animals.

Life in the Cambrian Period

In the huge burst of evolution creatures including microscopic organisms, sponges, starfish, sea urchins, sea lilies and velvet worms all evolved in this period. The first shelled animals also appeared; trilobites and brachiopods who then dominated the seas. Later in the period molluscs and primitive fish evolved. Trilobites were a major step in the evolution because they had the first eyes.

Plant Life in the Cambrian Period

In the Cambrian seas the only plant life was primitive algae and seaweeds.

Precambrian Era

The Precambrian Period starts with the birth of Earth to the appearance of many-celled animals, about 570 million years ago.

Methane and other gases were the only gases in the Earth primitive atmosphere. These gases dissolved into the masses of water which covered the Earth, forming a complex chemical "soup". Lighting discharges on this soup acted in a way that caused the chemicals to react, forming more complex chemicals very similar to the ones in living cells. After a few million years these chemicals developod the ability to reproduce. In the soup there was also fat globules. If the soup was stirredviolently by the wind, the complex chemicals may have become trapped within the fat globules. In time these structures evolved into lining cells surrounded by fatty membranes.

Life in the Precrambrian seas

Some of the first life in the sea was stromatolites, which appear to be made up of lots of rings of limestone, with orgaic layers in between.

Later life in these sea saw a range of soft body creatures, including jellyfish, worms and leaf like sea pens.

The only evidice left from that period where trace fossils left by the animal.

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