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The Cambrian Period was an important part in the history of life on Earth. The animals were complex, multicellular organisms that for the first time, started to appear mineralized (fossilized.) Some animals examples would be; inarticulate brachiopods, trilobites, and helicoplacoids. Also, Rodinia started breaking a part.
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The Ordovician Period is known for its diverse marine invertebrates and for the presence of the condonts, also known as early vertebrates. Some examples of animals would be; Articulate Brachiopods, Tabulate Corals, and Cephalopods.
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Corals reefs made first appearance during the Silurian Period, this was also a remarkable time in the evolution of fishes. We have evidence of life on land, including relatives of spiders and centipedes, and the earliest fossils of vascular plants. Some examples of animals were; sponges, stromatolites, and graptolites.
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The Devonian Period also known as the "Age of Fish"; brachiopods, ammonites, and new kinds of fish flourished in the oceans. The placoderms began dominating almost every known aquatic environment, the tetrapods and the arthropods began adapting to walking on land and, in the oceans, primitive sharks became more numerous. By the end of the Devonian, ferns, horsetails, glass sponges, and seed plants had appeared, producing the first trees and the firsts forests.
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The Carboniferous Period had one of the greatest evolutionary innovations, 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. Some examples would be; Dragonflies, Crinoids, and Tree ferns.
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During the Permian Period, the land of the continents became together to form Pangea; 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. Some examples of animals would be; Therapsids, Seymouria, and Glossopteris.
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The organisms of the Triassic Period included the holdovers from the Permian extinction, as well as the appearance of ichthyosaurs, pterosaurs, and modern conifers. The global climate was mostly hot and dry, with deserts spanning much of Pangaea's interior. However, the climate changed and became more humid as Pangaea began to drift apart. The end of the period was marked by another major mass extinction, that wiped out many groups and allowed dinosaurs to assume dominance in the Jurassic.
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The Jurassic Period, also known as the "Age of Reptiles". The fauna was dominated by dinosaurs. The first birds also appeared having evolved from a branch of theropod dinosaurs.Other major events were the appearance of the earliest lizards, and the evolution of therian mammals (including primitive placentals) Crocodriles moved from the terrestial life to the aquatic mode of life. Oceans were full of fish, squid, and coiled ammonites, along with great ichthyosaurs and long-necked plesiosaurs.
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The Cretaceous Period was a warm climate period, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now -extinct marine reptiles, ammonites and rudists, while dinosaurs continued to dominate on land. During this time, it also appeared new groups of mammals, birds, and flowering plants. This Period ended with the Cretaceous-Paleogene extinction event, a large mass extinction in which many groups died out.
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The Tertiary Period 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. Some examples of animals would be teleost fishes, grasses, and artiodactyls & perissodactyls.
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The Quaternary Period is typically defined by the cyclic growth and the decay of continental ice sheets associated with environmental changes that occured. During this 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 started to be covered by glaciers and then uncovered during the warmer interglacial periods.
