Ordovician The Ordovician r d v n is a geologic period and system, the second of six periods of the Paleozoic Era.The Ordovician spans . million years from the end of the Cambrian Period . million years ago Mya to the start of the Silurian Period . Mya. The Ordovician, named after the Celtic tribe of the Ordovices, was defined by Charles Lapworth in to resolve a Ordovician Period Major Events, Extinction, Facts Ordovician Period Ordovician Period, in geologic time, the second period of the Paleozoic Era It began . million years ago and ended . million years ago The interval was a time of intense diversification an increase in the number of species of marine animal life in what became known as the Ordovician radiation. Geologic Time Virtual Fossil Museum Geologic Time is divided and subdivided into various categories as presented here Eons are divided into Eras Eras are divided Periods Periods and subperiods are divided into Epochs Ordovician Period Paleoclimate Britannica Ordovician Period Paleoclimate Numerical climate models as well as carbon isotope measurements from preserved Ordovician soils suggest that atmospheric levels of carbon dioxide during the period were times higher than today These high levels were driven by widespread volcanic activity, which would have released large volumes of carbon dioxide into the atmosphere. Cambrian Ordovician extinction event The Cambrian Ordovician extinction event occurred approximately million years ago.This early Phanerozoic Eon extinction event eliminated many brachiopods and conodonts, and severely reduced the number of trilobite species. It was preceded by the less documented but probably worse End Botomian extinction event around million years ago and the Dresbachian extinction event about Paleozoic Era Paleobiology Fossil The Paleozoic Periods Cambrian Ordovician Silurian Devonian Carboniferous Permian The Paleozoic meaning time of ancient life Era lasted from to million years ago, and is A Sea without Fish Life in the Ordovician Sea of the A Sea without Fish Life in the Ordovician Sea of the Cincinnati Region Life of the Past Steven M Holland, Richard Arnold Davis, David L Meyer on FREE shipping on qualifying offers The region around Cincinnati, Ohio, is known throughout the world for the abundant and beautiful fossils found in limestones and shales that were deposited as sediments on the sea floor during the Trilobite Geological Time Scale The chart above gives an indication of the relationships of the trilobite orders, and their extent over geological time The Cambrian origin and proliferation of trilobites is very apparent, as well as the loss of the orders Agnostida, Ptychopariida, and Asaphida in the Ordovician, the loss of the majority of remaining orders in the late Devonian, and the final extinction of the class in the Some Trilobites of the Cincinnatian Dry Dredgers Some Trilobites of the Cincinnatian by Rich Fuchs, Dry Dredgers Trilobites are extinct members of the Arthropod family which were quite common in the Paleozoic sea waters that covered what is now the area in and around Cincinnati, Ohio. By John Tate Cincinnati Dry Dredgers By John Tate Retrorsirostra carleyi Brachiopods are marine bottom dwelling, suspension feeding, multicelled animals They have a soft body enclosed in two shells that can be opened to feed.