Devonian

adj. of or pertaining to Devon (district in England); pertaining to a period in the Paleozoic era (Geology)

n. period in the Paleozoic era during which there was dominance of fish and the first amphibians appeared (Geology)

For the Celtic language, see Southwestern Brythonic language; for the residents of the English county, see Devon.The Devonian is a geologic period of the Paleozoic era spanning from roughly 416 to 359 million years ago. It is named after Devon, England, where rocks from this period were first studied.During the Devonian Period, which occurred in the Paleozoic era, the first fish evolved legsand started to walk on land as tetrapods around 365 Ma, and the first insects and spiders also started to colonize terrestrial habitats.
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Noun
1. from 405 million to 345 million years ago; dominance of fishes and appearance of amphibians and ammonites
(synonym) Devonian period, Age of Fishes
(hypernym) period, geological period
(part-holonym) Paleozoic, Paleozoic era

(n.)
The Devonian age or formation.
  

(a.)
Of or pertaining to Devon or Devonshire in England; as, the Devonian rocks, period, or system.
  

408-362 Million Years Ago
As the Paleozoic era continues, we see the first appearance of land creatures, such as mites, ammonites, crabs, ground insects, and spiders. Towards the end of the Devonian period, amphibians began to colonize the land. The first ferns also and true seed plants eventually emerge. The Devonian period also saw many groups of a fishes evolve.
see list of time periods