Devonian Time
the Devonian Period - 410 to 360 million years ago

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Devonian Period:
Denoting Significant Events in:
Evolution, the Fossil Record,
Paleontology and Paleobiology

 

 

 

 

 




Devonian
(410 to 360 mya)
Epoch
Age
Mass extinction (F-F)
Land is colonized by plants and animals.
Appearances include: insects; sharks; amphibians (tetrapods); lung fishes and earliest seed plants.
Extensive radiation of fishes.
 Upper Devonian Famennian (>367ma)
Fransnian (>377ma)
 Middle Devonian Givetian (>381ma)
Eifelian (>386ma)
  Lower Devonian Emsian (>390ma)
Pragian (>396ma)
Lochovian (>410ma)

The seas swarmed with many kinds of unique fish during Devonian time. In fact, fishes were the only vertebrates on Earth until the Upper Devonian. Because of the extensive radiation of fishes, the Devonian is often called the age of fishes. Throughout the Devonian while the ancient jawless fish and placoderms remained, new more advanced forms were appearing. Devonian fish were some of the first vertebrates to evolve, and can be grouped into five classes: 1) agnatha or "jawless fish"; 2) spiny fish; 3) Placoderms or "platedskins"; 4) Chondrichthyes or otherwise known as sharks, and; 5) the bony fishes. Many of the armored fish became extinct at the end of the Devonian, and the lobe-finned fishes and lungfishes markedly declined. The cartilaginous fish, sharks and rays were likely the last group of fish to evolve.

The earliest animals with backbones were the class known as Agnathas that are most commonly called "jawless fish". Most of these fish had "shell skins" and lived in rivers and lakes from 510-350 million years ago. As scavengers, they sucked in water containing food perticles through slots in their heads.

The first trees appeared in the Devonian, and had developed the vascular system to grow to some 20 feet tall by the end of the Devonian. Also appearing were the Lycopods (scale trees and club mosses) that reproduced by means of spores; these went on to thrive through the Carboniferous but met extinction by the end of the Paleozoic.

The Devonian seas were filled with brachiopods, and by tabulate and rugose corals that built large bioherms, or reefs, in shallow waters. In the Lower Devonian, ammonoids appeared, leaving large limestone deposits from their shells. Bivalves, crinoid and blastoid echinoderms, graptolites, and trilobites were all present, though most groups of trilobites disappeared by the close of the Devonian.

Two major animal groups colonized the land. The first tetrapods, or four legged land-living vertebrates, appeared during the Devonian, as did the first terrestrial arthropods, including wingless insects and the earliest arachnids.