Portal:Devonian

The Devonian Portal

A map of Earth as it appeared 390 million years ago during the Middle Devonian Epoch

The Devonian (/dəˈvoʊni.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 419.62 million years ago (Ma), to the beginning of the succeeding Carboniferous period at 358.86 Ma. It is the fourth period of both the Paleozoic and the Phanerozoic. 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 be called 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

From top to bottom and left to right, examples of sarcopterygians: Guiyu oneiros, West Indian Ocean coelacanth, Australian lungfish and the tetrapodomorph Panderichthys rhombolepis.

Sarcopterygii (/ˌsɑːrkɒptəˈrɪdʒi.aɪ/; from Ancient Greek σάρξ (sárx) 'flesh' and πτέρυξ (ptérux) 'wing, fin')—sometimes considered synonymous with Crossopterygii (κροσσός, krossós, 'fringe')—is a clade (traditionally a class or subclass) of vertebrate animals which includes a group of bony fish commonly referred to as lobe-finned fish. These vertebrates are characterised by prominent muscular limb buds (lobes) within their fins, which are supported by articulated appendicular skeletons. This is in contrast to the other clade of bony fish, the Actinopterygii, which have only skin-covered bony spines supporting the fins.

The tetrapods, a mostly terrestrial clade of vertebrates, are now recognized as having evolved from sarcopterygian ancestors and are most closely related to lungfishes. Their paired pectoral and pelvic fins evolved into limbs, and their foregut diverticulum eventually evolved into air-breathing lungs. Cladistically, this would make the tetrapods a subgroup within Sarcopterygii and thus sarcopterygians themselves. As a result, the phrase "lobe-finned fish" normally refers to not the entire clade but only aquatic members that are not tetrapods, i.e. a paraphyletic group.

Non-tetrapod sarcopterygians were once the dominant predators of freshwater ecosystems during the Carboniferous and Permian periods, but suffered significant decline after the Great Dying. The only known extant non-tetrapod sarcopterygians are the two species of coelacanths and six species of lungfishes. (Full article...)

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

Selected Devonian land plant article

Reconstruction of Rhynia gwynne-vaughanii

The rhyniophytes are a group of extinct early vascular plants that are considered to be similar to the genus Rhynia, found in the Early Devonian (around 420 to 393 million years ago). Sources vary in the name and rank used for this group, some treating it as the class Rhyniopsida, others as the subdivision Rhyniophytina or the division Rhyniophyta. The first definition of the group, under the name Rhyniophytina, was by Banks, since when there have been many redefinitions, including by Banks himself. "As a result, the Rhyniophytina have slowly dissolved into a heterogeneous collection of plants ... the group contains only one species on which all authors agree: the type species Rhynia gwynne-vaughanii". When defined very broadly, the group consists of plants with dichotomously branched, naked aerial axes ("stems") with terminal spore-bearing structures (sporangia). The rhyniophytes are considered to be stem group tracheophytes (vascular plants). (Full article...)

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

Selected Devonian formation

The Oriskany Sandstone is a Middle Devonian age unit of sedimentary rock found in eastern North America. The type locality of the unit is located at Oriskany Falls in New York. The Oriskany Sandstone extends throughout much of the Appalachian Basin.

The unit name usage by the U.S. Geological Survey (USGS) is the Oriskany Sandstone. Butts (1940) stated that the Oriskany Sandstone "corresponds exactly with the Ridgely Sandstone" and that the rules of stratigraphic nomenclature dictate that the name Oriskany Sandstone should be applied to these strata. (Full article...)

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

Selected Devonian fish article

Teeth of Platycephalichthys, in CosmoCaixa Barcelona

Tristichopterids (Tristichopteridae) were a diverse and successful group of fish-like tetrapodomorphs living throughout the Middle and Late Devonian. They first appeared in the Eifelian stage of the Middle Devonian. Within the group sizes ranged from a few tens of centimeters (Tristichopterus) to several meters (Hyneria and Eusthenodon).

Some tristichopterids share some of the features of the elpistostegalians, a diverse clade of tetrapodomorphs close to the origin of (and including) tetrapods.^{[better source needed]} This mainly concerns the shape of the skull and a reduction in size of the posterior fins.

An old and persistent notion is that Eusthenopteron was able to crawl onto land using its fins. However, there is no evidence actually supporting this idea. All tristichopterids had become extinct by the end of the Late Devonian. (Full article...)

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

Selected Devonian invertebrate

Various gastropods from different types: black slug (a slug), Haliotis asinina (an abalone), Cornu aspersum (a land snail), Notarchus indicus (a seahare), Patella vulgata (a limpet), and Polycera aurantiomarginata (a nudibranch).

Gastropods (/ˈɡæstrəpɒdz/), commonly known as slugs and snails, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (/ɡæsˈtrɒpədə/).

This class comprises snails and slugs from saltwater, freshwater, and from the land. There are many thousands of species of sea snails and slugs, as well as freshwater snails, freshwater limpets, land snails and slugs.

The class Gastropoda is a diverse and highly successful class of mollusks within the phylum Mollusca. It contains a vast total of named species, second only to the insects in overall number. The fossil history of this class goes back to the Late Cambrian. As of 2017^[update], 721 families of gastropods are known, of which 245 are extinct and appear only in the fossil record, while 476 are currently extant with or without a fossil record. (Full article...)