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Cambrian Period
it is the time when most of the major groups of animals first appear in the fossil record. This event is sometimes called the "Cambrian Explosion," because of the relatively short time over which this diversity of forms appears. -
Ordovician
The Ordovician is best known for its diverse marine invertebrates, including graptolites, trilobites, brachiopods, and the conodonts (early vertebrates). A typical marine community consisted of these animals, plus red and green algae, primitive fish, cephalopods, corals, crinoids, and gastropods. -
Silurian
The Paleozoic era's Silurian period saw animals and plants finally emerge on land. But first there was a period of biological regrouping following the disastrous climax to the Ordovician. -
Devonian
The Rhynie Chert in Scotland is a Devonian age deposit containing fossils of both zosterophylls and trimerophytes, some of the earliest vascular plants. This indicates that prior to the start of the Devonian, the first major radiations of plants had already happened -
Carboniferous
The term "Carboniferous" comes from England, in reference to the rich deposits of coal that occur there. These deposits of coal occur throughout northern Europe, Asia, and midwestern and eastern North America. -
Permian
The distinction between the Paleozoic and the Mesozoic is made at the end of the Permian in recognition of the largest mass extinction recorded in the history of life on Earth. -
Trassic
Triassic was a time of transition. It was at this time that the world-continent of Pangaea existed, altering global climate and ocean circulation. The Triassic also follows the largest extinction event in the history of life, and so is a time when the survivors of that event spread and recolonized. -
Jurrasic
By the beginning of the Jurassic, the supercontinent Pangaea had begun rifting into two landmasses, Laurasia to the north and Gondwana to the south. This created more coastlines and shifted the continental climate from dry to humid, and many of the arid deserts of the Triassic were replaced by lush rainforests. -
Cretaceous
The Cretaceous is usually noted for being the last portion of the "Age of Dinosaurs", but that does not mean that new kinds of dinosaurs did not appear then. It is during the Cretaceous that the first ceratopsian and pachycepalosaurid dinosaurs appeared. -
Tertiary
Tertiary is an officially deprecated but still widely used term for a geologic period from 65 million to 1.806 million years ago, a time span that lies between the superseded Secondary period and the Quaternary. -
Quaternary
relating to, or being the geological period from the end of the Tertiary to the present time or the corresponding system of rocks
