In the geological timescale, the Llandovery epoch (from 443.7 ± 1.5 million years ago to 428.2 ± 2.3 million years ago) occurred during the Silurian period. The table and timeline of geologic periods presented here is in accordance with the dates and nomenclature proposed by the International Commission on Stratigraphy. ... The Silurian is a major division of the geologic timescale that extends from the end of the Ordovician period, about 443. ...
The Llandovery epoch is subdivided into three stages: Rhuddalian, Aeronian and Telychian. In the geologic timescale, the Aeronian is the age of the Llandovery epoch of the Silurian period of the Paleozoic era of the Fanerozoic eon that is comprehended between 439 million and 436 million years ago, approximatedly. ...
For example, the boundary between the Cretaceous period and the Palaeogene period is defined by the extinction event that marked the demise of the dinosaurs and of many marine species.
British geologists were also responsible for the grouping of periods into Eras and the subdivision of the Tertiary and Quaternary periods into epochs.
When William Smith and Sir Charles Lyell first recognized that rock strata represented successive time periods, there was no way to determine what time scale they represented.
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