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2019-11-21 08:37:28.0 [tstevens] Insert Concept
add narrower relation (DEVONIAN [866fbfc3-7395-4a77-bc1e-29272e8b795c,396453] - UPPER
[d6b9b49c-667e-4da7-bd72-32b4b5d89c0e,423453]);
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2019-11-21 08:37:39.0 [tstevens] Insert Concept
add narrower relation (DEVONIAN [866fbfc3-7395-4a77-bc1e-29272e8b795c,396453] - MIDDLE
[62e5494d-c515-47dc-a4af-f870874add3d,423457]);
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2019-11-21 08:37:48.0 [tstevens] Insert Concept
add narrower relation (DEVONIAN [866fbfc3-7395-4a77-bc1e-29272e8b795c,396453] - LOWER
[599af9b7-4517-45c2-8505-a46fc204e524,423461]);
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2019-12-17 10:54:55.0 [tstevens]
insert Definition (id: null
text: The Devonian is a geologic period and system of the Paleozoic, spanning 60 million
years from the end of the Silurian, 419.2 million years ago (Mya), to the beginning
of the Carboniferous, 358.9 Mya. The first significant adaptive radiation of life
on dry land occurred during the Devonian. 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 Fishes. The placoderms
began dominating almost every known aquatic environment. The ancestors of all four-limbed
vertebrates (tetrapods) began adapting to walking on land, as their strong pectoral
and pelvic fins gradually evolved into legs. In the oceans, primitive sharks became
more numerous than in the Silurian and Late Ordovician. The first ammonites, species
of molluscs, appeared. Trilobites, the mollusc-like brachiopods and the great coral
reefs, were still common. The Late Devonian extinction which started about 375 million
years ago severely affected marine life, killing off all placodermi, and all trilobites,
save for a few species of the order Proetida.
language code: en);
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| definition |
The Devonian is a geologic period and system of the Paleozoic, spanning 60 million
years from the end of the Silurian, 419.2 million years ago (Mya), to the beginning
of the Carboniferous, 358.9 Mya. The first significant adaptive radiation of life
on dry land occurred during the Devonian. 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 Fishes. The placoderms
began dominating almost every known aquatic environment. The ancestors of all four-limbed
vertebrates (tetrapods) began adapting to walking on land, as their strong pectoral
and pelvic fins gradually evolved into legs. In the oceans, primitive sharks became
more numerous than in the Silurian and Late Ordovician. The first ammonites, species
of molluscs, appeared. Trilobites, the mollusc-like brachiopods and the great coral
reefs, were still common. The Late Devonian extinction which started about 375 million
years ago severely affected marine life, killing off all placodermi, and all trilobites,
save for a few species of the order Proetida.
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