Phanerozoic Column

Abstract

This page provides a simple stratigraphic column depicting the Phanerozoic, with a few points of interest recorded. As usual, more to come ... one day.

Keywords: Phanerozoic, Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian, Triassic, Jurassic, Cretaceous, Tertiary, Quaternary, Ediacaran fauna, trilobites, graptolites, mass extinction

Acknowledgement: This page and the dependent ‘period’ pages are dedicated to Ruben Arthur Stirton (1901-1966), and owe their inspiration to his 1959 classic, Time, Life and Man.

Introduction

...

Periods of the Phanerozoic

Quaternary

Ice ages; the emergence of modern mammalian faunas, including man.

Tertiary

Mammalian radiation, particularly at the Paleocene/Eocene boundary, when several groups of mammals abruptly appeared on the Holarctic continents following the dispersal of groups from Asia to North America and Europe; primates become established and the earliest fully bipedal human ancestor known, the 4 Ma old Australopithecus afarensis, is first recognised from the famous fossil known as Lucy.

Cretaceous

Diversification of the angiosperms from beginnings probably near the Jurassic-Cretaceous boundary. The end of the period is marked by one of the more profound mass extinction events of the Phanerozoic; many groups of living things died out, most famously the dinosaurs. A meterorite impact at the end of the period may have been a contributing factor, though to what extent is still unknown.

Jurassic

Although the dinosaurs evolved in the Triassic, and most of the major dinosaur lineages probably date back to then, the Jurassic was the period in which they spectacularly radiated and spread to all parts of the globe. Focus On: Dinosaurs

Triassic

During the Triassic the tetrapods diversified widely: mammals, crocodiles, pterosaurs, dinosaurs, lizards, and snakes all evolved from primitive reptilian ancestors during the Triassic.

Permian

Trilobites finally become extinct, probably before the mass extinction which ends the period. Insects develop metamorphosis. Reptiles diversify and give rise to the mammal-like reptiles. The Permian ends with the greatest mass extinction event known. Focus On: Mass Extinctions

Carboniferous

Trilobites are almost extinct but one order, the Proetida, survives into the Permian. Crinoids abundant; ammonites diversify; sharks and bony fish common; insects evolve wings; amphibians spread and become specialised. The first reptiles evolve. Extensive forests give rise - mainly in the Late Carboniferous (Pennsylvanian) - to the great coal swamps of Europe and North America.

Devonian

Fishes are the dominent animals; scale tree forests appear on land, inhabited by the first wingless insects; blastoids are at their peak; the first ammonites and amphibians evolve.

Silurian

First coral reefs widespread; eurypterids at their peak; fish diversify, evolving lower jaws and invading fresh water environments; lycopsid land plants appear and early terrestrial ecosystems are established.

Ordovician

The Ordovician saw the origin and rapid evolution of many new types of invertebrate animals which replaced their Cambrian predecessors. Primitive vascular plants appeared the land, until then almost totally barren. Graptolites, cystoids and nautiloids are at their peak, and trilobites undergo a second radiation. Jawless fishes emerge. Focus On: Graptolites

Cambrian

In the sediments of Cambrian age, fossils ‘suddenly’ become common for the first time. This effect, which has come to be known as the “Cambrian Explosion,” has guaranteed the Cambrian Period a special place in the hearts and minds of generations of paleontologists. Archaeocyathids are abundant, trilobites are at their peak, and there is evidence of some very early land plants. Focus On: Trilobites

Precambrian Time

Vendian - The Last Precambrian Period

At the end of the Varanger ice age, perhaps the most profound such event known, the first signs of complex life begin to appear in the fossils record. The earliest probable metazoan body fossils are thought to be cnidarians, from the ~600 Ma (million years old) Twitya Formation in Canada. Somewhat younger, perhaps 590 to 565 Ma, the Doushantuo phosphate deposit in China has yielded probable algae, sponges, cnidarians and bilaterians. Towards the end of the period, about 565 Ma, the classical Ediacaran assemblages emerge and persist through into the Cambrian. Focus On: Ediacarans