The Devonian is also known as the Age of Fishes, since several major fish lineages evolved at this time. Sea levels were high and the global climate was warm. Sea surface temperatures in the tropics averaged 30 Celsius, much like the warmer parts of the Pacific today. Growth rings from corals living during the Devonian period have provided evidence that there were more than 365 days in the year back then - about 404 at the start of the period, falling to 396 by the end.
Began: 417 million years ago
Late Devonian mass extinction
354 million years ago
Once thought barren, the Devonian ended with plants and animals exploiting a new ecosystem: swamp.
Dr Ted Daeschler, Philadelphia Academy of Natural Sciences and Prof Keith Thompson, Oxford University Museum talk about the Devonian environment and the world's first swamps. Programme first transmitted in 2001.
Reconstruction of the Earth in the Devonian period, 417 million - 354 million years ago. Credit: Dr Ron Blakey, NAU Geology.
During this period the following events are thought to have contributed to the Late Devonian mass extinction.
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 419.2 ± 3.2 Mya (million years ago), to the beginning of the Carboniferous Period, about 358.9 ± 0.4 (ICS, 2004). It is named after Devon, England, where rocks from this period were first studied.
The Devonian period experienced the first significant adaptive radiation of terrestrial life. Since large vertebrate terrestrial herbivores had not yet appeared, free-sporing vascular plants began to spread across dry land, forming extensive forests which covered the continents. By the middle of the Devonian, several groups of plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants appeared. Various terrestrial arthropods also became well-established. Fish reached substantial diversity during this time, leading the Devonian to often be dubbed the "Age of Fish". The first ray-finned and lobe-finned bony fish appeared, while the placoderms began dominating almost every known aquatic environment.
The ancestors of all tetrapods began adapting to walking on land, their strong pectoral and pelvic fins gradually evolved into legs. In the oceans, primitive sharks became more numerous than in the Silurian and the late Ordovician. The first ammonite mollusks appeared. Trilobites, the mollusk-like brachiopods and the great coral reefs, were still common. The Late Devonian extinction severely affected marine life, killing off all placoderms, and all trilobites, save for a few species of the order Proetida.
The paleogeography was dominated by the supercontinent of Gondwana to the south, the continent of Siberia to the north, and the early formation of the small continent of Euramerica in between.
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