Devonian Period
A Devonian Period is a geologic period that spanned 60 million years from the end of the Silurian Period (419.2 ± 3.2 Mya) to the beginning of the Carboniferous Period (358.9 ± 0.4. Mya).
- Context:
- It likely included the evolution of Insects.
- … functional fin to proto-leg.
- …
- See: Paleozoic, Lignin, Pteridophyte, Vascular Plant, Coal Field, Forest, Vertebrate, Paleozoic, Silurian, Adaptive Radiation, Pteridophyte, Vascular Plant.
References
2018
- (Wikipedia, 2018) ⇒ https://en.wikipedia.org/wiki/Devonian Retrieved:2018-2-21.
- The Devonian is a geologic period and system of the Paleozoic, spanning 60 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, where rocks from this period were first studied.
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 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 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 mollusk-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.
The palaeogeography 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.
- The Devonian is a geologic period and system of the Paleozoic, spanning 60 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, where rocks from this period were first studied.
2015
- https://www.thegwpf.org/patrick-moore-should-we-celebrate-carbon-dioxide/
- QUOTE: … The Devonian Period beginning 400 million years ago marked the culmination of the invasion of life onto the land. Plants evolved to produce lignin, which in combination with cellulose, created wood which in turn for the first time allowed plants to grow tall, in competition with each other for sunlight. As vast forests spread across the land living biomass increased by orders of magnitude, pulling down carbon as CO2 from the atmosphere to make wood. Lignin is very difficult to break down and no decomposer species possessed the enzymes to digest it. Trees died atop one another until they were 100 metres or more in depth. This was the making of the great coal beds around the world as this huge store of sequestered carbon continued to build for 90 million years. Then, fortunately for the future of life, white rot fungi evolved to produce the enzymes that can digest lignin and coincident with that the coal-making era came to an end. …