Ordovician period dating

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Some cystoids (primitive stalked marine animals related to modern starfish and sand dollars) and crinoids (called sea lilies and feather stars; also related to starfish and sand dollars) appeared.

Green algae were common in the Ordovician and Late Cambrian (perhaps earlier). The first terrestrial plants appeared in the form of tiny plants resembling liverworts.

In what was to become North America and Europe, the Ordovician period was a time of shallow continental seas rich in life.

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As the southern supercontinent Gondwana drifted over the South Pole, ice caps formed on it, which have been detected in Upper Ordovician rock strata of North Africa and then-adjacent northeastern South America, which were south-polar locations at the time.Further elaboration of the fossil evidence provided the basis for subdividing the period.The Ordovician Period is usually broken into Early (Tremadoc and Arenig), Middle (Llanvirn, subdivided into Abereiddian and Llandeilian), and Late (Caradoc and Ashgill) epochs.Fossil spores from land plants have been identified in uppermost Ordovician sediments.The first land fungi probably appeared in the Latest Ordovician, following the appearance of plants.

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