Silurian

The Silurian (/sɪˈljʊəriən, s-/ sih-LYOOR-ee-ən, sy-)[8][9][10] is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at 443.8 million years ago (Mya), to the beginning of the Devonian Period, 419.2 Mya.[11] The Silurian is the shortest period of the Paleozoic Era. As with other geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by a few million years. The base of the Silurian is set at a series of major Ordovician–Silurian extinction events when up to 60% of marine genera were wiped out.

Silurian
443.8 ± 1.5 – 419.2 ± 3.2 Ma
Plate tectonics of Earth during the early Silurian
Chronology
Etymology
Name formalityFormal
Synonym(s)Gotlandian
Usage information
Celestial bodyEarth
Regional usageGlobal (ICS)
Time scale(s) usedICS Time Scale
Definition
Chronological unitPeriod
Stratigraphic unitSystem
First proposed byRoderick Murchison, 1835
Time span formalityFormal
Lower boundary definitionFAD of the Graptolite Akidograptus ascensus
Lower boundary GSSPDob's Linn, Moffat, UK
55.4400°N 3.2700°W / 55.4400; -3.2700
GSSP ratified1984[4][5]
Upper boundary definitionFAD of the Graptolite Monograptus uniformis
Upper boundary GSSPKlonk, Czech Republic
49.8550°N 13.7920°E / 49.8550; 13.7920
GSSP ratified1972[6]
Atmospheric and climatic data
Sea level above present dayAround 180m, with short-term negative excursions[7]

One important event in this period was the initial establishment of terrestrial life: vascular plants emerged from more primitive land plants, dikaryan fungi started expanding and diversifying along with glomeromycotan fungi, and three groups of arthropods (myriapods, arachnids and hexapods) became fully terrestrialized.

A significant evolutionary milestone during the Silurian was the diversification of jawed fish and bony fish.


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