Each of the eras can be further divided into several periods.
Click on each period to find out more.
|During the Quaternary Period mammoths and mastodons, sabre-toothed cats, giant ground sloths, and many other large mammals roamed North America, Asia, and Europe. Much of the world's temperate zones were alternately covered by glaciers and then uncovered during the warmer interglacial periods.|
|The Tertiary Period, following a major extinction, is marked by the flourishing of flowering plants, grasslands, insects, teleost fish, and birds, as well as the mammals for which it is usually noted.|
|During the Cretaceous the first ceratopsian and pachycephalo- saurid dinosaurs appeared, and we find the first fossils of many insect groups, modern mammal and bird groups, and the first flowering plants. However, the end of the Cretaceous brought the end of many previously successful groups of organisms, such as non-avian dinosaurs and ammonites.|
|Great plant-eating dinosaurs roamed the earth, feeding on lush growths of ferns and palm-like cycads. Smaller but vicious carnivores stalked the great herbivores. Oceans were full of fish, squid, and coiled ammonites, along with great ichthyosaurs and long-necked plesiosaurs.|
|The organisms of the Triassic included the holdovers from the Permian extinction (club mosses and “mammal-like” reptiles), as well as the appearance of icthyosaurs (marine reptiles), pterosaurs, and modern conifers.|
|During the Permian, the land continents came together to form Pangaea; reptiles diversified; and the great forests of fern-like plants shifted to gymnosperms, plants with their offspring enclosed within seeds. The end of the Permian marked the largest mass extinction recorded in the history of life on Earth.|
|The term "Carboniferous" comes from England, in reference to the rich deposits of coal that occur there. One of the greatest evolutionary innovations of the Carboniferous was the amniote egg, which allowed the ancestors of birds, mammals, and reptiles to reproduce on land. We also see an increase in large insects and tree ferns.|
|By the end of the Devonian, ferns, horsetails and seed plants had appeared, producing the first trees and the first forests. Also during the Devonian, two major animal groups, the tetrapods and the arthropods, colonized the land, while brachiopods, ammonites, and new kinds of fish flourished in the oceans.|
|Coral reefs made their first appearance during the Silurian, and this was also a remarkable time in the evolution of fishes. We also have evidence of life on land, including relatives of spiders and centipedes, and the earliest fossils of vascular plants.|
|The Ordovician is known for its diverse marine invertebrates and for the presence of the conodonts (early vertebrates).|
|The Cambrian Period marks an important point in the history of life on Earth. It is the time when most of the major groups of animals first appear in the fossil record.|