page_title: Ordovician
section_title: Fauna
hierarchical_section_title: Ordovician / Fauna
caption_attribution_description: English: Orthoceras sp., nautiloid from the middle Ordovician. Digital.
context_page_description: The Ordovician is the second period of the Paleozoic era. It lasted from about 485.4 million years ago to 443.4 mya. It follows the Cambrian period and is followed by the Silurian period.
  The Ordovician was named after the Welsh tribe of the Ordovices. It was defined by Charles Lapworth in 1879. He recognized that the fossils in the disputed strata were different from those of the Cambrian or the Silurian. Therefore, he reasoned, they should be placed in a period of their own.
  Recognition of the Ordovician period was slow in Britain, but elsewhere it was quickly accepted. In 1906 it was adopted as an official period of the Paleozoic era by the International Geological Congress.
  The Ordovician ended with a series of extinction events that, together amount to the second greatest extinction of the Phanerozoic. This was the End–Ordovician extinction event.
context_section_description: For most of the Ordovician, life continued to flourish, but near the end of the period the End–Ordovician extinction event seriously affected planktonic forms like conodonts, graptolites, and some groups of trilobites. Brachiopods, bryozoans and echinoderms were also heavily affected, and the cone-shaped nautiloids died out completely, except for rare Silurian forms.
  The extinctions may have been caused by an ice age that occurred at the end of the Ordovician period: the end of the Ordovician was one of the coldest times in the last 600 million years of earth history.
caption: Nautiloids like Orthoceras were among the largest predators in the Ordovician.
exif: {}