Llandovery Epoch

Llandovery
443.8 ± 1.5 – 433.4 ± 0.8 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Map of Earth as it appeared 440 million years ago during the Llandovery epoch, Aeronian stage[citation needed]
Chronology
−444 — – −442 — – −440 — – −438 — – −436 — – −434 — – −432 — – −430 — – −428 — – −426 — – −424 — – −422 — – −420 — – −418 — Paleozoic O Silurian D Late O Llandovery Wenlock Ludlow Přídolí Early D Rhuddanian Aeronian Telychian Sheinwoodian Homerian Gorstian Ludfordian             ← Lau event ← Mulde event[1] ← Ireviken event[2] Subdivision of the Silurian according to the ICS, as of 2021.[3] Vertical axis scale: millions of years ago.
Etymology
Name formality	Formal
Name ratified	1984
Usage information
Celestial body	Earth
Regional usage	Global (ICS)
Time scale(s) used	ICS Time Scale
Definition
Chronological unit	Epoch
Stratigraphic unit	Series
Time span formality	Formal
Lower boundary definition	FAD of the Graptolite Akidograptus ascensus
Lower boundary GSSP	Dob's Linn, Moffat, UK 55°26′24″N 3°16′12″W / 55.4400°N 3.2700°W / 55.4400; -3.2700
Lower GSSP ratified	1984[4][5]
Upper boundary definition	Imprecise. Currently placed between acritarch biozone 5 and last appearance of Pterospathodus amorphognathoides. See text for more info.
Upper boundary definition candidates	A conodont boundary (Ireviken datum 2) which is close to the murchisoni graptolite biozone.
Upper boundary GSSP candidate section(s)	None
Upper boundary GSSP	Hughley Brook, Apedale, UK 52°34′52″N 2°38′20″W / 52.5811°N 2.6389°W / 52.5811; -2.6389
Upper GSSP ratified	1980[6]

In the geological timescale, the Llandovery Epoch (from 443.8 ± 1.5 million years ago to 433.4 ± 0.8 million years ago) occurred at the beginning of the Silurian Period. The Llandoverian Epoch follows the massive Ordovician-Silurian extinction events, which led to a large decrease in biodiversity and an opening up of ecosystems.

Widespread reef building started in this period and continued into the Devonian Period when rising water temperatures are thought to have bleached out the coral by killing their photo symbionts.

The Llandoverian Epoch ended with the Ireviken event which killed off 50% of trilobite species, and 80% of the global conodont species.