| Palaeos: Paleozoic | |
Late ordovician epoch |
| Ordovician period | Hirnantian Age |
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Paleozoic Era Cambrian Period Ordovician Period Early Ordovician Epoch Middle Ordovician Epoch Late Ordovician Epoch Sandbian Age Katian Age Hirnantian Age Silurian Period Llandovery Epoch Rhuddanian Age Aeronian Age Telychian Age Wenlock Epoch Ludlow Epoch Přídolí Epoch Devonian Period Carboniferous Period Permian Period |
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The Ordovician has been quite significantly revised in recent
years. The traditional division of the Late Ordovician into the Caradoc
and Ashgill has been replaced by a three-part division. The first two ages
of the Late Ordovician are unnamed, and are referred to as Ordovician V and
VI. Sandbian is equivalent to the Early and Middle Caradoc. Ordovician VI
is equivalent to the Late Caradoc and Early Ashgill. The Hirnantian,
formerly a stage of the Ashgill, is now the final age of the
Ordovician. ATW040316
 Platystrophia laticosta Horizon: Maysville Group (early Hirnantian epoch - Pusgillian Age)Locality: southern USA Size: shell about 2 to 2.5 cm wide Links:  More
on Platystrophia (at the Union
College Geology Department site)
|
 Rafinesquina loxorhytis Horizon: RichmondianLocality: Indiana Weight: Size: shell about 7 cm wide Links: more
on Rafinesquina (at the Union
College Geology Department site)
|
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