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

Partially reconstructed D. terrelli skull and trunk armor (specimen CMNH 5768), Cleveland Museum of Natural History

Dunkleosteus is an extinct genus of large arthrodire ("jointed-neck") fish that existed during the Late Devonian period, about 382–358 million years ago. It was a pelagic fish inhabiting open waters, and one of the first apex predators of any ecosystem.

Dunkleosteus consists of ten species, some of which are among the largest placoderms ("plate-skinned") to have ever lived: D. terrelli, D. belgicus, D. denisoni, D. marsaisi, D. magnificus, D. missouriensis, D. newberryi, D. amblyodoratus, D. raveri, and D. tuderensis. The largest and best known species is D. terrelli. Since body shape is not known, various methods of estimation put the living total length of the largest known specimen between 4.1 to 10 m (13 to 33 ft) long and weigh around 1–4 t (1.1–4.4 short tons). However, lengths of 5 metres (16 ft) or more are poorly supported and the most extensive analyses support smaller size estimates.

Dunkleosteus could quickly open and close its jaw, creating suction like modern-day suction feeders, and had a bite force that is considered the highest of any living or fossil fish, and among the highest of any animal. Fossils of Dunkleosteus have been found in North America, Poland, Belgium, and Morocco. (Full article...)

List of selected Devonian articles
Sarcopterygii Trilobites Marcellus Formation Late Devonian extinction Acadian Orogeny Bactritida List of Early Devonian land plants

Selected Devonian land plant article

Bark fragment from Sigillaria mamillaris sp. Estonian Museum of Natural History, Tallinn, Estonia.

Sigillaria is a genus of extinct, spore-bearing, arborescent lycophyte, known from the Carboniferous and Permian periods. It is related to the more famous Lepidodendron, and more distantly to modern quillworts. (Full article...)

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

Selected Devonian formation

Windom shale member of the Moscow formation, a trilobite pygidium (Eldredgeops rana) is exposed but not clearly visible

The Windom shale or Windom member is a member of the Moscow formation in New York. It preserves fossils going back to the Givetian stage of the middle Devonian. The Windom shale is widely known for its high quality trilobite fossils. (Full article...)

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

Selected Devonian fish article

Scaumenacia curta & Bothriolepis canadensis

Scaumenacia is an extinct genus of prehistoric lungfish. It lived around the Devonian in North America alongside another prehistoric lungfish: Fleurantia. It lived from approximately 384 to 376 millions of years ago. (Full article...)

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

Selected Devonian invertebrate

Ostracods, or ostracodes, are a class of the Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 33,000 species (only 13,000 of which are extant) have been identified, grouped into 7 valid orders. They are small crustaceans, typically around 1 mm (0.04 in) in size, but varying from 0.2 to 30 mm (0.008 to 1 in) in the case of the marine Gigantocypris. The largest known freshwater species is Megalocypris princeps, which reach 8mm in length. In most cases, their bodies are flattened from side to side and protected by a bivalve-like valve or "shell" made of chitin, and often calcium carbonate. The family Entocytheridae and many planktonic forms do not have calcium carbonate. The hinge of the two valves is in the upper (dorsal) region of the body. Ostracods are grouped together based on shell and soft part morphology. While early work indicated the group may not be monophyletic and early molecular phylogeny was ambiguous on this front, recent combined analyses of molecular and morphological data suggested monophyly in analyses with broadest taxon sampling, but this monophyly had no or very little support (Fig. 1 - bootstrap 0, 17 and 46, often values above 95 are considered sufficient for the taxon support). They have a wide range of diets, and the class includes carnivores, herbivores, scavengers and filter feeders, but most ostracods are deposit feeders. (Full article...)