Devonian

The Devonian is a geologic period and system of the Paleozoic Era spanning roughly 419 to 359 million years ago. It follows the Silurian Period and precedes the Carboniferous. The name derives from Devon, England, where rocks of this age were first studied.

During the Devonian, life diversified dramatically. Known as the Age of Fishes, it saw major diversification of jawed fishes, including armored placoderms, and the rise of early lobe-finned and ray-finned fishes, as well as early sharks. On land, terrestrial ecosystems developed for the first time: vascular plants formed extensive forests and thick soils; the first trees and seed-bearing plants appeared, with Archaeopteris among the earliest tree-like plants.

Invertebrates and reef communities also diversified, with corals contributing to reef ecosystems. The late Devonian marks the emergence of early tetrapods, the first vertebrates capable of living on land, with fossils such as Acanthostega and Ichthyostega representing transitional forms toward terrestrial amphibians.

Toward the end of the period, the Frasnian–Famennian extinction event caused major faunal turnover and reef loss, signaling a biotic crisis and prompting shifts in marine and terrestrial faunas. The Devonian spans about 60 million years and is subdivided into Early (Lower), Middle, and Late (Upper) Devonian.