Portal:Devonian

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The Devonian Portal

Map of the Earth during the late Devonian, c. 370 Ma.

The Devonian (/dɪˈvoʊni.ən, dɛ-/ də-VOH-nee-ən, deh-) is a geologic period and system of the Paleozoic era during the Phanerozoic eon, spanning 60.3 million years from the end of the preceding Silurian period at 419.2 million years ago (Ma), to the beginning of the succeeding Carboniferous period at 358.9 Ma. It is named after Devon, South West England, where rocks from this period were first studied.

The first significant evolutionary radiation of life on land occurred during the Devonian, as free-sporing land plants (pteridophytes) began to spread across dry land, forming extensive coal forests which covered the continents. By the middle of the Devonian, several groups of vascular plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants (pteridospermatophytes) appeared. This rapid evolution and colonization process, which had begun during the Silurian, is known as the Silurian-Devonian Terrestrial Revolution. The earliest land animals, predominantly arthropods such as myriapods, arachnids and hexapods, also became well-established early in this period, after beginning their colonization of land at least from the Ordovician period.

Fishes, especially jawed fish, reached substantial diversity during this time, leading the Devonian to often be dubbed the Age of Fishes. The armored placoderms began dominating almost every known aquatic environment. In the oceans, cartilaginous fishes such as primitive sharks became more numerous than in the Silurian and Late Ordovician. Tetrapodomorphs, which include the ancestors of all four-limbed vertebrates (i.e. tetrapods), began diverging from freshwater lobe-finned fish as their more robust and muscled pectoral and pelvic fins gradually evolved into forelimbs and hindlimbs, though they were not fully established for life on land until the Late Carboniferous. (Full article...)

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Selected Devonian Article

The list of Early Devonian (419.2 ± 2.8 to 393.3 ± 2.5 million years ago) land plants includes currently known vascular and potentially vascular plants, along with some possibly non-vascular plants, that have been described from global Early Devonian fossil assemblages. (Full article...)

List of selected Devonian articles
Sarcopterygii Trilobites Marcellus Formation Late Devonian extinction Acadian Orogeny Bactritida Dunkleosteus

Selected Devonian land plant article

Archaeopteris fossil leaves

The progymnosperms are an extinct group of woody, spore-bearing plants that is presumed to have evolved from the trimerophytes, and eventually gave rise to the gymnosperms, ancestral to acrogymnosperms and angiosperms (flowering plants). They have been treated formally at the rank of division Progymnospermophyta or class Progymnospermopsida (as opposite). The stratigraphically oldest known examples belong to the Middle Devonian order the Aneurophytales, with forms such as Protopteridium, in which the vegetative organs consisted of relatively loose clusters of axes. Tetraxylopteris is another example of a genus lacking leaves. In more advanced aneurophytaleans such as Aneurophyton these vegetative organs started to look rather more like fronds, and eventually during Late Devonian times the aneurophytaleans are presumed to have given rise to the pteridosperm order, the Lyginopteridales. In Late Devonian times, another group of progymnosperms gave rise to the first really large trees known as Archaeopteris. The latest surviving group of progymnosperms is the Noeggerathiales, which persisted until the end of the Permian.

Other characteristics:

Vascular cambium with unlimited growth potential is present as well as xylem and phloem.
Ancestors of the earliest seed plants as well as the first true trees.

Strong monopodial growth is exhibited. (Full article...)

List of selected Devonian articles
pteridophytes Sigillaria Pteridospermatophyta Lycophyte Equisetidae Rhyniophyte Trimerophytopsida Lycopodiopsida

Selected Devonian formation

The Grey Downtonian facies occurs in the Downton Castle Sandstone Group of the British Old Red Sandstone, and more or less straddles the Devonian-Silurian boundary. The Ludlow Bone Bed and Temeside Shales are sometimes also included in the Grey Downtonian, which is also referred to as the Temeside group, part of the Downton Series. It is intermediate between the marine flagstones beneath it and the terrestrial deposits above it. The beds were deposited in a marine environment, with some material being washed in from the nearby land. (Full article...)

List of selected Devonian formation articles
Tully Formation Hamilton Group Tioga Bentonites Windom shale Rhinestreet Formation Oriskany Formation Bakken formation Traverse Group New Albany Shale Old Red Sandstone

Selected Devonian fish article

Holotype fossil and interpretive drawing of Tinirau clackae

Tinirau is an extinct genus of sarcopterygian fish from the Middle Devonian of Nevada. Although it spent its entire life in the ocean, Tinirau is a stem tetrapod close to the ancestry of land-living vertebrates in the crown group Tetrapoda. Relative to more well-known stem tetrapods, Tinirau is more closely related to Tetrapoda than is Eusthenopteron, but farther from Tetrapoda than is Panderichthys. The type and only species of Tinirau is T. clackae, named in 2012. (Full article...)

List of selected Devonian fish articles
Ctenaspis Brochoadmones Cheirolepis Holoptychius Hyneria Lepidaspis Scaumenacia Placoderm Diplocercides Dipterus Elpistostegalia Gooloogongia Ventastega Tristichopteridae Phoebodus Stethacanthidae Xenacanthus

Selected Devonian invertebrate

Pentremites godoni, a blastoid from the Lower Carboniferous of Illinois.

Blastoids (class Blastoidea) are an extinct type of stemmed echinoderm, often referred to as sea buds. They first appear, along with many other echinoderm classes, in the Ordovician period, and reached their greatest diversity in the Mississippian subperiod of the Carboniferous period. However, blastoids may have originated in the Cambrian. Blastoids persisted until their extinction at the end of Permian, about 250 million years ago. Although never as diverse as their contemporary relatives, the crinoids, blastoids are common fossils, especially in many Mississippian-age rocks. (Full article...)