Ordovician

The Ordovician ( /ɔrdəˈvɪʃən/) is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 485.4 ± 1.9 to 443.4 ± 1.5 million years ago (ICS, 2004). It follows the Cambrian Period and is followed by the Silurian Period. The Ordovician, named after the Celtic tribe of the Ordovices, was defined by Charles Lapworth in 1879 to resolve a dispute between followers of Adam Sedgwick and Roderick Murchison, who were placing the same rock beds in northern Wales into the Cambrian and Silurian periods respectively. Lapworth, recognizing that the fossil fauna in the disputed strata were different from those of either the Cambrian or the Silurian periods, realized that they should be placed in a period of their own. While recognition of the distinct Ordovician Period was slow in the United Kingdom, other areas of the world accepted it quickly. It received international sanction in 1960, when it was adopted as an official period of the Paleozoic Era by the International Geological Congress.

Life continued to flourish during the Ordovician as it did in the Cambrian, although the end of the period was marked by a significant mass extinction. Invertebrates, namely mollusks and arthropods, dominated the oceans. Fish, the world's first true vertebrates, continued to evolve, and those with jaws may have first appeared late in the period. Life had yet to diversify on land.

Read more about Ordovician:  Dating, Subdivisions, Paleogeography, Geochemistry, Climate and Sea Level, Life, End of The Period

Other articles related to "ordovician":

Actinoceras - Related Genera
... Kochoceras, named by Troedsson, 1926, is a middle to upper Ordovician actinocerid similar overall to Actinoceras but with the shell flattened on the venter and ... Kochoceras was first discovered in northern Greenland, which during the Ordovician was near equatorial ... Saffordoceras comes from the Middle Ordovician of eastern North America ...
Lituitida
... have their beginnings in the Early Ordovician with forms like Ancistroceras ... following the early Cincinnatian (Sandbian) in the early Late Ordovician, from which the group never recovers ... One genus, Holmiceras, is limited to the Lower Ordovician and one, Ancistroceras, comes from both the lower and middle of the period ...
List Of Mapped Rock Formations In Pennsylvania
... Srh Silurian Tuscarora Formation St Silurian Shawangunk Formation Ss Ordovician Juniata Formation Oj Ordovician Bald Eagle Formation Obe Ordovician Reedsville Formation Or Ordovician Martinsburg Formation Om ...
Ordovician - End of The Period
... The Ordovician came to a close in a series of extinction events that, taken together, comprise the second largest of the five major extinction events in Earth's history in terms of percentage of genera ... years ago and mark the boundary between the Ordovician and the following Silurian Period ... ended the long, stable greenhouse conditions typical of the Ordovician ...
Canadian Epoch - Background
... At that time the Ordovician had not yet been recognized ... as roughly equivalent to the Beekmantown strata of the Lower Ordovician ... facies (Flower 1957) whereas those in the remaining Ordovician are more local in nature and the two facies are more integrated ...