Part of the Paleozoic Era
Silurian Period - Devonian Period - Carboniferous Period
The Devonian Period is the fourth period of the Paleozoic Era and of the Phanerozoic Eon. The period begins at the time from which the earliest Monograptus uniformis graptolite fossils in Bed 20 of the Klonk Section, located near modern Prague, Czech Republic are known, and ends at the time from which the earliest Siphonodella sulcata conodonts are known.
Three continents existed during the Devonian: the supercontinents Gondwana and Euramerica, and the smaller continent of Siberia. Euramerica had begun to form during the Silurian as the smaller continents of Avalonia, Baltica, and Laurasia began to collide, and the process was completed during the earlier part of this period. The Caledonian orogeny continued, and Gondwana and the new Euramerica began to meet in the early stages of the formation of Pangaea and further rose the Appalachian Mountains. The ocean known as Panthalassa was by far the largest of the time, though smaller oceans existed and included the Paleo-Tethys, Proto-Tethys, Rheic, and Ural oceans.
Life on land would finally diversify, as large forest formed, sometimes covering entire continents. The first ray-finned (Actinopterygii) and lobe-finned (Sarcopterygii) fish evolved during the Devonian, while bony (Osteichthyes) and cartilaginous (Chondrichthyes) fish further diversified. The first abundant shark genus, Cladoselache, evolved, as did fish with fins that resembled primitive legs such as Tiktaalik. The infamous armored fish, Dunkleosteus, is also known from the Devonian. Apart from fish, other Devonian marine species included the first ammonites, and the already existing brachiopods and coral reefs. Though the period is best known for its marine life, and large-scale marine extinction known as the Late Devonian extinction event was staged during the later part of the period.
The Devonian is subdivided into three epochs: the Early Devonian, the Middle Devonian, and the Late Devonian.
Devonian Timescale:
Devonian Period - 419.2-358.9 MYA
-Early Devonian Epoch - 419.2-393.3 MYA
--Lockhovian Age - 419.2-410.8 MYA
--Pragian Age - 410.8-407.6 MYA
--Emsian Age - 407.6-393.3 MYA
-Middle Devonian Epoch - 393.3-382.7 MYA
--Eifelian Age - 393.3-387.7 MYA
--Givetian Age - 387.7-382.7 MYA
-Late Devonian Epoch - 382.7-358.9 MYA
--Frasnian Age - 382.7-372.2 MYA
--Famennian Age - 372.2-358.9 MYA