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

Marcellus shale exposure above Marcellus, N.Y. The vertical joints create sheer cliff faces.

The Marcellus Formation or the Marcellus Shale is a Middle Devonian age unit of sedimentary rock found in eastern North America. Named for a distinctive outcrop near the village of Marcellus, New York, in the United States, it extends throughout much of the Appalachian Basin.

The unit name usage by the U.S. Geological Survey (USGS) includes Marcellus Shale and Marcellus Formation. The term "Marcellus Shale" is the preferred name throughout most of the Appalachian region, although the term "Marcellus Formation" is also acceptable within the State of Pennsylvania. The unit was first described and named as the "Marcellus shales" by J. Hall in 1839. (Full article...)

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

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

The Tully Formation is a geologic unit in the Appalachian Basin. The Tully was deposited as a carbonate rich mud, in a shallow sea at the end of the Middle Devonian. Outcrops for the Tully are found in New York State and Pennsylvania. It is also found subsurface in western Maryland and northern West Virginia. A number of fossil remains from marine organisms maybe found in Tully out crops. (Full article...)

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

Selected Devonian fish article

C. dentata

Ctenaspis (Ctenaspis kaieri) is an extinct genus of heterostracan cyathaspid agnathans from the early Devonian of Canada, Norway and Russia 416.0 to 412.3 million years ago. Species of Ctenaspis are typically 10 to 18 cm long with the max length being 40 cm long. The genus contains only one known species, namely Ctenaspis kaieri.

C. kaieri has no adorbital opening and only two dorsal and ventral plates . The dorsal plate is fused with branchials and the plates notably thin. C. kiaeri has its branchial openings located at the posterior edge of armour. The dorsal shield is flat. (Full article...)

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

Selected Devonian invertebrate

Solitary rugose coral Grewingkia canadensis in three views; Ordovician, Indiana

The rugosa, also called the tetracorallia or horn coral, are an extinct order of solitary and colonial corals that were abundant in Middle Ordovician to Late Permian seas.

Solitary rugosans (e.g., Caninia, Lophophyllidium, Neozaphrentis, Streptelasma) are often referred to as horn corals because of a unique horn-shaped chamber with a wrinkled, or rugose, wall. Some solitary rugosans reached nearly a meter in length. However, some species of rugose corals could form large colonies (e.g., Lithostrotion). When radiating septa were present, they were usually in multiples of four, hence Tetracorallia in contrast to modern Hexacorallia, colonial polyps generally with sixfold symmetry.

Rugose corals have a skeleton made of calcite that is often fossilized. Like modern corals (Scleractinia), rugose corals were invariably benthic, living on the sea floor or in a reef-framework. Some symbiotic rugose corals were endobionts of Stromatoporoidea, especially in the Silurian period. Although there is no direct proof, it is inferred that these Palaeozoic corals possessed stinging cells to capture prey. They also had tentacles to help them catch prey. Technically they were carnivores, but prey-size was so small they are often referred to as microcarnivores. (Full article...)