geology Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Ea ...

, the Arenig (or Arenigian) is a time interval during the Ordovician period and also the suite of rocks which were deposited during this interval.

History

The term was first used by

Adam Sedgwick Adam Sedgwick (; 22 March 1785 – 27 January 1873) was a British geologist and Anglican priest, one of the founders of modern geology. He proposed the Cambrian and Devonian period of the geological timescale. Based on work which he did on W ...

in 1847 with reference to the "Arenig Ashes and Porphyries" in the neighbourhood of Arenig Fawr, in Merioneth, North Wales. The rock-succession in the Arenig district has been recognized by W. G. Fearnsides (“On the Geology of Arenig Fawr and Moel Llanfnant", Q.J.G.S. vol. lxi., 1905, pp. 608–640, with maps). The above succession is divisible into: # A lower series of gritty and calcareous sediments, the "Arenig Series" as it is now understood; # A middle series, mainly volcanic, with shale, the " Llandeilo Series"; and # The shale and limestones of the

Bala Bala may refer to: Places India *Bala, India, a village in Allahabad, India * Bala, Ahor, a village in the Jalore district of Rajasthan * Bala, Raebareli, a village in Uttar Pradesh, India Romania * Bala, Mehedinți, a commune in Mehedinţi ...

or Caradoc Stage. It was to the middle series (2) that Sedgwick first applied the term "Arenig". In the typical region and in North Wales generally the Arenig series appears to be unconformable upon the

Cambrian The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ag ...

rocks; this is not the case in South Wales. The Arenig series is represented in North Wales by the

Garth Grit Garth may refer to: Places *Garth, Alberta, Canada *Garth, Bridgend, a village in south Wales :* Garth railway station (Bridgend) *Garth, Ceredigion, small village in Wales *Garth, Powys, a village in mid Wales :* Garth railway station (Powys) *Ga ...

and Ty Obry beds, by the Shelve series of the

Corndon Corndon Hill ( cy, Cornatyn) is a hill in Powys, Mid Wales, whose isolated summit rises to 1,683 ft above sea level. It is surrounded on three sides by the England, English county of Shropshire and forms a prominent landmark in the Wales-E ...

district, the Skiddaw Slates of the Lake District, the Ballantrae Group of

Ayrshire Ayrshire ( gd, Siorrachd Inbhir Àir, ) is a Counties of Scotland, historic county and registration county in south-west Scotland, located on the shores of the Firth of Clyde. Its principal towns include Ayr, Kilmarnock and Irvine, North Ayrshi ...

, and by the

Ribband Series A ribbon or riband is a thin band of material, typically cloth but also plastic or sometimes metal, used primarily as decorative binding and tying. Cloth ribbons are made of natural materials such as silk, cotton, and jute and of synthetic ...

of slates and shale in

Wicklow Wicklow ( ; ga, Cill Mhantáin , meaning 'church of the toothless one'; non, Víkingaló) is the county town of County Wicklow in Ireland. It is located south of Dublin on the east coast of the island. According to the 2016 census, it has ...

and

Wexford Wexford () is the county town of County Wexford, Ireland. Wexford lies on the south side of Wexford Harbour, the estuary of the River Slaney near the southeastern corner of the island of Ireland. The town is linked to Dublin by the M11/N1 ...

. It may be mentioned here that the " Llanvirn" Series of

H. Hicks H is the eighth letter of the Latin alphabet. H may also refer to: Musical symbols * H number, Harry Halbreich reference mechanism for music by Honegger and Martinů * H, B (musical note) * H, B major People * H. (noble) (died after 1 ...

was equivalent to the bifidus shale and the Lower Llandeilo Series.

Geochronology

In the

geologic timescale The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geoch ...

, the Arenig or Arenigian refers to an age of the Early Ordovician epoch, between 477.7 and 470 million years ago, contemporary with the

Floian The Floian is the second stage of the Ordovician Period. It succeeds the Tremadocian with which it forms the Lower Ordovician epoch. It precedes the Dapingian Stage of the Middle Ordovician. The Floian extended from to million years ago. The ...

of the

ICS ICS may refer to: Computing * Image Cytometry Standard, a digital multidimensional image file format used in life sciences microscopy * Industrial control system, computer systems and networks used to control industrial plants and infrastructu ...

, based on a section in Sweden ( Diabasbrottet quarry) and with the same boundaries. The Arenig and Floian rocks are the upper part of the Lower Ordovician and follow the

Tremadocian The Tremadocian is the lowest stage of Ordovician. Together with the later Floian Stage it forms the Lower Ordovician Epoch. The Tremadocian lasted from to million years ago. The base of the Tremadocian is defined as the first appearance of the ...

( Gasconadian in North America) which is the lower part. Either is followed by the Middle Ordovician ICS Dapingian or by the Llanvirnian of older chronologies. The Arenig and equivalent Floian are represented in North America by the upper three stages of the

Canadian Canadians (french: Canadiens) are people identified with the country of Canada. This connection may be residential, legal, historical or cultural. For most Canadians, many (or all) of these connections exist and are collectively the source of ...

which is followed by the

Middle Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. T ...

Whiterockian which is the lower part of the now shortened Chazyan.

Events

The Arenig rocks were deposited during a sudden worldwide rise in sea level resulting in widespread

marine transgression A marine transgression is a geologic event during which sea level rises relative to the land and the shoreline moves toward higher ground, which results in flooding. Transgressions can be caused by the land sinking or by the ocean basins filling ...

. The early Ordovician surge in marine diversity also began around this time.

Brachiopod fauna

;''

Incertae sedis ' () or ''problematica'' is a term used for a taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertain ...

brachiopod Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, ...

s of the Floian *''Eurorthisina'' *''Tegulella'' ;

Acrotretida Acrotretida is an extinct order of linguliform brachiopods in the class Lingulata. They lived from the Lower Cambrian to the Middle Devonian, with their peak diversity from the Middle Cambrian to the Ordovician. Acrotretida contains the sole ...

of the Floian *''Acanthambonia'' *'' Cyrbasiotreta'' *''Eoconulus'' *''Issedonia'' *'' Karnotreta'' *'' Lurgiticoma'' *'' Multispinula'' *'' Mylloconotreta'' *''Numericoma'' *''Orthisocrania'' *''Polylasma'' *'' Pomeraniotreta'' *''Pseudocrania'' *'' Scaphelasma'' *''Schizotreta'' *''Torynelasma'' ; Lingulida of the Floian *''Acanthorthis'' *''Aulonotreta'' *''Dictyobolus'' *''Ectenoglossa'' *'' Elliptoglossa'' *'' Monobolina'' *''Paldiskites'' *'' Paterula'' *'' Pseudolingula'' *'' Quasithambonia'' *'' Rafanoglossa'' *''Volborthia'' ; Orthida of the Floian *'' Acanthorthis'' *'' Acanthotoechia'' *'' Anchigonites'' *'' Angusticardinia'' *'' Anomalorthis'' *'' Antigonambonites'' *'' Apomatella'' *'' Astraborthis'' *'' Crossiskenidium'' *''Dalmanella'' *'' Desmorthis'' *''Diparelasma'' *'' Eodiorthelasma'' *''Eosotrematorthis'' *''

Estlandia ''Estlandia'' is a Gonambonitidae, gonambonitid genus. It is one of the endemic brachiopod, brachiopods in the Ordovician of Baltoscandia. Currently, eight different species and subspecies of the genus have been recorded from the Aseri to Keila ...

'' *'' Euorthisina'' *'' Famatinorthis'' *'' Fasciculina'' *'' Ferrax'' *'' Ffynnonia'' *'' Fistulogonites'' *'' Glossorthis'' *''Glypterina'' *'' Hesperonomiella'' *'' Incorthis'' *'' Jaanussonites'' *'' Ladogiella'' *''Lomatorthis'' *'' Monorthis'' *'' Munhella'' *'' Nereidella'' *''

Neumania ''Neumania'' is a genus of mites belonging to the family Unionicolidae. The genus has cosmopolitan distribution In biogeography, cosmopolitan distribution is the term for the range of a taxon that extends across all or most of the world in ...

'' *'' Nocturneilla'' *'' Notoscaphidia'' *'' Oligorthis'' *'' Orthambonites'' *'' Orthidiella'' *'' Orthidium'' *''

Orthis Orthoidea is a superfamily of brachiopods containing the families: * Family Orthidae * Family Anomalorthidae * Family Bohemiellidae * Family Glyptorthidae * Family Hesperonomiidae * Family Hesperorthidae * Family Lycophoriidae * Family Nan ...

'' *'' Oslogonites'' *'' Panderina'' *'' Paralenorthis'' *'' Paurorthina'' *'' Paurorthis'' *'' Phragmorthis'' *''

Platystrophia ''Platystrophia'' is an extinct genus of brachiopods that lived from the Ordovician to the Silurian in Asia, Europe, North America, and South America. It has a prominent sulcus and fold. It usually lived in marine lime mud and sands. Distrib ...

'' *'' Platytoechia'' *'' Polytoechia'' *'' Pomatotrema'' *'' Prantlina'' *'' Productorthis'' *'' Progonambonites'' *'' Protohesperonomia'' *'' Protoskenidiodes'' *'' Pseudomimella'' *'' Raunites'' *'' Rhynchorthis'' *'' Shoshonorthis'' *'' Sinorthis'' *'' Taphrorthis'' *''

Tarfaya Tarfaya ( ar, طرفاية - ''Ṭarfāya''; ber, ⵟⵔⴼⴰⵢⴰ) is a coastal Moroccan town, located at the level of Cape Juby, in western Morocco, on the Atlantic coast. It is located about 890 km southwest of the capital Rabat, an ...

'' *'' Treioria'' *'' Trematorthis'' *'' Valcourea'' *'' Virgoria'' ; Paternida of the Floian *'' Dictyonites'' ; Pentamerida of the Floian *'' Acanthorthis'' *'' Acanthoglypha'' *'' Boreadocamara'' *'' Camerella'' *'' Doloresella'' *'' Hesperotrophia'' *'' Idiostrophia'' *'' Imbricatia'' *'' Karakulina'' *'' Liricamera'' *'' Lycophoria'' *'' Porambonites'' *'' Rectotrophia'' *''

Rosella Rosellas are in a genus that consists of six species and nineteen subspecies. These colourful parrots from Australia are in the genus ''Platycercus''. ''Platycercus'' means "broad-tailed" or "flat-tailed", reflecting a feature common to the ...

'' *'' Rugostrophia'' *'' Stenocamara'' *''

Syntrophia The Syntrophales are an order of Thermodesulfobacteriota The Thermodesulfobacteriota are a phylum of thermophilic sulfate-reducing bacteria. A pathogenic intracellular thermodesulfobacteriote has recently been identified. Phylogeny The phyl ...

'' *'' Syntrophinella'' *'' Xenelasma''

Strophomenida

; Strophomenida of the Floian *'' Acanthorthis'' *'' Ahtiella'' *'' Aporthophyla'' *'' Borua'' *'' Calyptolepta'' *'' Christiania'' *''

Ingria Ingria is a historical region in what is now northwestern European Russia. It lies along the southeastern shore of the Gulf of Finland, bordered by Lake Ladoga on the Karelian Isthmus in the north and by the River Narva on the border with E ...

'' *'' Leptestia'' *'' Petroria'' *'' Plectambonites'' *'' Reinversella'' *'' Schedophyla'' *''Taffia'' *'' Tourmakeadia'' ; Trimerellida of the Floian *'' Dinobolus''

Cephalopoda

;

Actinocerida The Actinocerida are an order of generally straight, medium to large cephalopods that lived during the early and middle Paleozoic, distinguished by a siphuncle composed of expanded segments that extend into the adjacent chambers, in which deposit ...

*'' Metactinoceras'' *'' Ordosoceras'' *''

Polydesmia ''Polydesmia'' is a genus of fungi within the family Hyaloscyphaceae The Hyaloscyphaceae are a family of fungi in the Helotiales order. Species in this family have a cosmopolitan distribution, and are saprobic, growing on dead wood and other p ...

Upper

The following is a list of Actinocerid genera whose fossils are geochronologically found first in ''upper Arenig strata''. These genera may survive into later portions of the Arenig stage, or even into later geological stages. This list should not be thought of in terms of the lifespan of the genera included. *''

Leurorthoceras ''Leurorthoceras'' is a genus of flattened actinoceratids with a siphuncle narrower than in ''Actinoceras ''Actinoceras'' is the principal and root genus of the Actinoceratidae, a major family in the Actinocerida, that lived during the Middl ...

'' *''

Nybyoceras ''Nybyoceras'' is an actinocerid genus assigned to the Armenoceratidae and similar to ''Armenoceras'' except for having a siphuncle close to the ventral side of the shell. Morphology As with ''Armenoceras'', ''Nybyoceras'' has a medium to large ...

'' *''

Actinoceras ''Actinoceras'' is the principal and root genus of the Actinoceratidae, a major family in the Actinocerida, that lived during the Middle and Late Ordovician. It is an extinct genus of nautiloid cephalopod that thrived in the warm waters of the Un ...

'' *'' Wutinoceras'' *''

Ormoceras ''Ormoceras'' is an actinocerid nautiloid genus and type for the family Ormoceratidae, found in North America from the late Chazyan through the early Cincinnatian of the Middle and Upper Ordovician, but which continued through the Devonian worl ...

'' *'' Adamsoceras'' *''Georgina''

Orthocerida

; Orthocerids of the Floian *''

Eobactrites ''Bactroceras'' is a genus of orthoceratoid cephalopods that lived during the early Middle Ordovician, from about 472—464 mya, existing for approximately 8 million years.Nautiloidea – Ellesmerocerida by W.M Furnish and Brian F. Glensister; ...

'' ; Barrandeocerida of the Floian *''

Plectoceras ''Plectoceras'' is a genus of nautiloids included in the tarphycerid suborder Barrandeocerina that lived during the Middle and Late Ordovician. It has been found widespread in the Middle and Upper Ordovician of North America. ''Plectoceras'' has ...

'' ;

Ellesmerocerida The Ellesmerocerida is an order of primitive cephalopods belonging to the subclass Nautiloidea with a widespread distribution that lived during the Late Cambrian and Ordovician. Morphology The Ellesmerocerida are characterized by shells that ...

of the Floian *'' Amsleroceras'' *'' Apocrinoceras'' *'' Avoceras'' *'' Bakeroceras'' *''

Baltoceras ''Baltoceras'' is a member of the ''Ellesmerocerida'', included in the family, ''Baltoceratidae''. The shell of ''Baltoceras'' is slender with a subcircular cross section, straight transverse sutures, and a large siphuncle in contact with the v ...

'' *'' Catoraphinoceras'' *''

Cochlioceras ''Cochlioceras'' is an extinct baltoceratid genus from the lower and middle Ordovician (Arenig - Llanvrin) of what are now Europe, the U.S (Vermont), and China, having existed for approximately 14 million years, from about 478 to 464 mya.Teicher ...

'' *'' Copiceras'' *'' Clelandoceras'' *'' Cumberloceras'' *'' Cyclostomiceras'' *''

Cyrtobaltoceras ''Cyrtobaltoceras'' is an extinct cephalopod genus known from the upper Lower Ordovician Fort Cassin Formation at Valcour, N.Y. that is included in the Nautiloid family Baltoceratidae Taxonomy ''Cyrtobaltoceras'' was named by Flower (1964 who ...

'' *'' Desioceras'' *'' Diaphoroceras'' *'' Diastoloceras'' *'' Dwightoceras'' *'' Dyscritoceras'' *'' Ectocycloceras'' *''

Endorioceras ''Endorioceras'' is an extinct genus of actively mobile carnivorous cephalopod of the family ''Baltoceratidae'' that lived in what would be North America during the Ordovician from 490–479 mya, existing for approximately . Taxonomy ''Endorioce ...

'' *'' Eocyckistomiceras'' *'' Eothinoceras'' *''

Hemichoanella The Genus ''Hemichoanella'' is a small, extinct, orthoconic nautiloid cephalopod from the Lower Ordovician of Western Australia assigned to the orthoceratoid family, ''Baltoceratidae''. ''Hemichoanella'' and the Baltoceratidae are part of the ...

'' *'' Irianoceras'' *'' Kyminoceras'' *''

Lawrenceoceras ''Lawrenceoceras'' is a genus of moderately curved, gently expanding bassleroceratids (Nautiloidia, Ellesmerocerida) from the Lower Ordovician of eastern North America. Septa dividing the chambers are close spaced; sutures straight, transverse; ...

'' *'' Meikeloceras'' *''

Microbaltoceras ''Microbaltoceras'' is an extinct genus of the cephalopod family Baltoceratidae that lived in what would be North America during the Early Ordovician. It was named by Rousseau Flower (1964) and assigned by him to the Baltoceratidae. The type s ...

'' *'' Monogonoceras'' *'' Ogygoceras'' *'' Pictetoceras'' *'' Protocycloceras'' *''

Quebecoceras ''Quebecoceras'' is an extinct genus from the nautiloid order Ellesmerocerida that lived during the Gasconadian Stage at the beginning of the Early Ordovician. ''Quebecoceras'' is a cyrtoconic, similar to ''Dakeoceras'' and ''Paradakeoceras'' ...

'' *''

Rangeroceras ''Rangeroceras'' is an extinct orthoceratoid cephalopod genus that lived in what is now western North America during the latter part of the Early Ordovician. Background Shells of ''Rangeroceras'' are smooth, slightly depressed, rod-bearing orth ...

'' *'' Rhabdiferous'' *''

Rioceras ''Rioceras'' is an extinct genus of orthocerid cephalopods of the family Baltoceratidae that lived in what would be North America during the Early Ordovician from 480—472 mya, existing for approximately 8 million years.R. H. Flower. 1964. The N ...

'' *'' Rudolfoceras'' *'' Smithvilloceras'' *''

Somalinautilus ''Somalinautilus'' is a genus of nautiloids that is found in the Middle to Upper Jurassic of England, France, and Somaliland. The genus contains three species, ''S. antiquus'', first assigned to ''Nautilus'' by Dacque in 1910, ''S. fuscus'', firs ...

'' *''

'' *'' Vassaroceras'' *''

Veneficoceras ''Veneficoceras'' is a genus of the rod-bearing Baltoceratidae, an extinct cephalopod family with characteristics of the orthoceratoid Dissidocerida, found in Cassinianage, Lower Ordovician, limestone in western Utah Utah ( , ) is a stat ...

'' *'' Ventroloboceras'' ;

Endocerida Endocerida is an extinct nautiloid order, a group of cephalopods from the Lower Paleozoic with cone-like deposits in their siphuncle. Endocerida was a diverse group of cephalopods that lived from the Early Ordovician possibly to the Late Siluri ...

*''

Campendoceras ''Campendoceras'' is a genus of proterocameroceratids from the Lower Ordovician of NW Australia and possibly Estonia that can be recognized by its slender, weakly endogastric, longiconic and annulate shell and large marginal siphuncle that con ...

'' *'' Dartonoceras'' *'' Kaipingoceras'' *'' Kugeloceras'' *'' Lobosiphon'' *'' Manitouoceras'' *'' Mcqueenoceras'' *'' Mysticoceras'' *'' Notocycloceras'' *'' Oderoceras'' *'' Parapiloceras'' *'' Phragmosiphon'' *'' Platysiphon'' *'' Pliendoceras'' *'' Retroclitendoceras'' *''

Stenosiphon ''Stenosiphon'' is the scientific name of two genera of organisms and may refer to: * ''Stenosiphon'' (cephalopod), a prehistoric genus of nautiloids * ''Stenosiphon'' (plant), a genus of plants in the family Onagraceae {{Genus disambiguatio ...

'' *'' Subpenhsioceras'' *'' Utoceras'' *'' Yorkoceras'' *'' Vaginoceras'' *'' Chisiloceras'' *'' Cyrtovaginoceras'' *'' Tallinnoceras'' *'' Juaboceras'' *'' Penhsioceras'' *'' Ventrolobendoceras'' ;Lower The following is a list of Endocerid genera whose fossils are geochronologically found first in ''lower Arenig strata''. These genera may survive into later portions of the Arenig stage, or even into later geological stages. This list should not be thought of in terms of the lifespan of the genera included. *'' Allopiloceras'' *'' Choreanoceroides'' *'' Escharendoceras'' *'' Lebetoceras'' *'' Loxochoanella'' *'' Sewardoceras'' *'' Telleroceras'' *'' Clitendoceras'' *'' Coreanoceras'' *''

Cotteroceras ''Cotteroceras'' is a genus of proterocameroceratids from the Lower Ordovician of North America and Siberia characterized by a long straight and compressed shell with very short camerae and long body chamber. Sutures are straight and oblique, s ...

'' *'' Piloceras'' *''

Endoceras ''Endoceras'' ( Ancient Greek for "inner horn") is an extinct genus of large, straight shelled cephalopods from the Middle and Upper Ordovician that gives its name to the Nautiloid order Endocerida. The cross section in the mature portion is sli ...

'' *'' Proterovaginoceras'' *'' Cyrtendoceras'' *''

Anthoceras ''Anthoceras'' is a genus of straight, annulated, proterocamerioceratids (Order Endocerida) from the Lower Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 ...

'' *'' Chaohuceras'' *''

Proterocameroceras ''Proterocameroceras'' is an early Endocerid from the upper Lower Ordovician belong to the Proterocameroceratidae The ''Proterocameroceratidae'' were the first of the Endocerida. They began early in the Ordovician with ''Proendoceras'' or simi ...

'' *'' Thylacoceras'' ;Upper The following is a list of Endocerid genera whose fossils are geochronologically found first in ''upper Arenig strata''. These genera may survive into later portions of the Arenig stage, or even into later geological stages. This list should not be thought of in terms of the lifespan of the genera included. *'' Allocotoceras'' *''

Cassinoceras ''Cassinoceras'' ("Cassin Horn") is a genus of nautiloids belonging to the endocerid family Piloceratidae that comes from the late Early Ordovician of eastern North America and adjacent territories.Teichert, Curt, 1964. Endoceratoidea ''in'' Treat ...

'' *'' Chihlioceras'' *'' Cyclocyrtendoceras'' *''

Cyptendoceras ''Cyptendoceras'' is an extinct nautiloid cephalopod included in the family Ellesmeroceratidae that lived in what would be North and South America during the latter part of the Early Ordovician (late Arenig) from about 475 – 472 mya, exist ...

'' *'' Kirkoceras'' *''

Lobendoceras ''Lobendoceras'' is a proterocameraceratid with a rather large, moderately expanded, straight shell with a large marginal siphuncle in which sutures have a broad, deep, ventral lobe and septal necks are subholochoanitic to holochoanitic. Lobe ...

'' *'' Najaceras'' *'' Protocyclendoceras'' *'' Yehlioceras'' *''

Nanno Nanno (german: Nain, Ladin: ''Nan'') was a '' comune'' (municipality) in Trentino in the northern Italian region Trentino-Alto Adige/Südtirol, located about north of Trento. As of 31 December 2004, it had a population of 623 and an area of ...

'' *'' Dideroceras'' *'' Lobocyclendoceras'' *'' Meniscoceras'' *'' Paracyclendoceras'' *'' Cacheoceras'' *'' Perkinsoceras'' *'' Williamsoceras'' *'' Manchuroceras'' *'' Schmidtoceras'' ; Intejocerida of the Floian *'' Bajkaloceras'' *'' Evencoceras'' *'' Intejoceras'' *'' Rossoceras'' ;

Oncocerids The Oncocerida comprise a diverse group of generally small nautiloid cephalopods known from the Middle Ordovician to the Mississippian (early Carboniferous; one possible member is known from the Early Permian), in which the connecting rings are ...

of the Floian *'' Phthanoncoceras'' *''

Valhalloceras ''Valhalloceras'' is a genus of nautiloid cephalopods found only in upper Lower Ordovician, Arenigian, carbonates on Svalbard Island and Jan Mayen Island. The type and only species so far named is ''Valhalloceras floweri'' Evans and King 199 ...

'' ; Nautiloids of the Floian *'' Buttsoceras'' *''

Centroonoceras ''Centroonoceras'' is a middle Ordovician cyrtoconic nautiloid cephalopod, otherwise similar to the orthoconic '' Sactorthoceras'' and also included in the Sactorthoceratidae. It was named by Kobayashi, 1934, and has been found in Korea and in ...

'' *''

Gangshanoceras ''Gangshanoceras'' is a fossil nautiloid cephalopod genus included in the orthocerid family Proteoceratidae Proteoceratidae is an extinct family of actively mobile aquatic carnivorous cephalopods belonging to the subclass Orthoceratoidea e ...

'' *''

Geisonoceras ''Geisonoceras'' is an extinct orthocerid genus named by Hyatt, 1884, and type for the Geisonoceratidae established by Zhuravleva in 1959. Fossil record Fossils of '' Geisonoceras'' are found in marine strata from the Ordovician until the Devon ...

'' *''

Glenisteroceras ''Glenesteroceras'', which is of questionable validity, is based on a single specimen from the Lower Ordovician of New York state, described by Rousseau Flower, 1957. ''Glenestoceras'' is described as being a weakly annulate orthocone with a cir ...

'' *''

Michelinoceras ''Michelinoceras'' is the oldest known genus of the Michelinocerida, more commonly known as the Orthocerida, characterized by long, slender, nearly cylindrical orthocones with a circular cross section, long camerae, very long body chambers, and a ...

'' *''

Orthoceras ''Orthoceras'' ("straight horn") is a genus of extinct nautiloid cephalopod restricted to Middle Ordovician-aged marine limestones of the Baltic States and Sweden. This genus is sometimes called ''Orthoceratites''. Note it is sometimes misspell ...

'' *'' Oxfordoceras'' *''

Rhynchorthoceras ''Rhynchorthoceras'' is a Middle Ordovician genus characterized by a rapidly expanded, weakly annulate orthocone, like the orthoconic section of ''Ancistroceras'', but with only a curved, cyrtoconic apex instead of juvenile whorls. ''Rhynchorth ...

'' *'' Stereoplasmoceras'' *''

Tajaroceras ''Tajaroceras'' is an extinct slender cephalopod from the uppermost Lower Ordovician of western North America, belonging to the Orthocerid family Troedssonellidae. Background The shell of ''Tajaroceras'' is smooth and straight. The siphuncle whi ...

'' *''

Wardoceras ''Wardoceras'' is an extinct nautiloid genus from the late Early Ordovician of Western Utah, assigned to the orthocerid family, Michelinoceratidae Background Shells of ''Wardoceras'' are smooth and orthoconic, with a circular cross section an ...

'' ;

Tarphycerida The Tarphycerida were the first of the coiled cephalopods, found in marine sediments from the Lower Ordovician (middle and upper Canad) to the Middle Devonian. Some, such as ''Aphetoceras'' and ''Estonioceras'', are loosely coiled and gyroconic; ...

*'' Deltoceras'' *'' Pseudancistroceras'' *'' Seelyoceras'' ;Lower *'' Alaskoceras'' *'' Moreauoceras'' *'' Pilotoceras'' *'' Shumardoceras'' *'' Pycnoceras'' *''

Campbelloceras ''Campbelloceras'' is a tarphyceratid nautiloid known from the Lower Ordovician, Upper Canadian Epoch of North America, where it is widespread. ''Campbelloceras'' was named by Ulrich and Foerste in 1936. The shell of ''Campbelloceras'' has a ci ...

'' *''

Aphetoceras ''Aphetoceras'' is a genus of tarphycerid cephalopod within the Estonioceratidae; loosely coiled without an impression along the dorsal margin; early whorls barely reaching, separating then diverging in the final mature whorl; weakly ribbed in s ...

'' ;Upper *''

Aethoceras ''Aethoceras'' is a genus of Tarphycerida Nautiloidea, nautiloids included in the family Estonioceratidae for which the shell is a loosely coiled, gradually expanding dextral torticone with a slightly depressed whorl section. Siphuncle small, ve ...

'' *'' Bentoceras'' *'' Centrotarphyceras'' *'' Clytoceras'' *'' Cycloplectoceras'' *'' Eichwaldoceras'' *'' Eurystomites'' *''

Hardmanoceras ''Hardmanoceras'' is a tarphycerid genus belonging to the Trocholitidae from the upper Lower Ordovician to possibly the lower Middle Ordovician, found in Western Australia. ''Hardmanoceras'' is like ''Discoceras ''Discoceras'' is an extinct m ...

'' *''

Holmiceras ''Holmiceras'' is one of two ancestral lituitids from the late Early Ordovician (Arenigian). The other being ''Ancistroceras''. ''Holmiceras'' begins with about 1.5 to 2 loosely coiled whorls followed by a rapidly expanding orthocone, much like ...

'' *'' Pionoceras'' *'' Trocholitoceras'' *'' Wichitoceras'' *''

Tarphyceras ''Tarphyeras'' is a genus of tarphyceratid with whorls rounded in cross section, having a deeply impressed dorsum and a ventral to subcentral siphuncle, known from the Lower Ord (U Canad) of North America. It differs from '' Campbelloceras'' in ...

'' *''

Litoceras ''Litoceras'' is a trocholitid (Tarphycerida) genus that has been found in the Lower and Middle Ordovician of Newfoundland. Whorls in ''Litoceras'' have a broadly rounded cross section with its width greater than its height. Litoceras somewhat ...

'' *''

Curtoceras ''Curtoceras'' is a genus in the tarphycerid family Trocholitidae found widespread in the late Early and Middle Ordovician of North America and northern Europe. ''Curtoceras'' has a shell that is gradually expanded, with half the fully mature bo ...

'' *'' Arkoceras'' *''

Estonioceras ''Estonioceras'' is an extinct genus of tarphyceridan nautiloids from the Ordovician of Europe. Sources * ''Dinosaur Encyclopedia'' by Jayne Parsons * ''Fossils'' (Smithsonian Handbooks) by David Ward External links''Estonioceras''in the Pa ...

'' *''

Tragoceras ''Isostigma'' is a genus of South American flowering plants in the Asteraceae, daisy family. ; Species References

Coreopsideae Asteraceae genera Flora of South America {{Coreopsideae-stub ...

Trilobite fauna

;Trilobites of the Floian *''

Canningella ''Canningella'' is an extinct genus of sponge in the family Anthaspidellidae Anthaspidellidae is an extinct family of sponges whose dendroclone spicules form ladder-like trab A trab is a structural element within a sponge formed by the fusion ...

'' *''

Gogoella ''Gogoella'' is an extinct genus of trilobite in the class Trilobita. There is one described species in ''Gogoella'', ''G. brevis''. Some place it in the family Pliomeridae Pliomeridae is a family of phacopide trilobites, containing ...

'' *'' Macrogrammus'' *''

Priceaspis ''Priceaspis'' is an extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, alt ...

'' *''

Thymurus ''Thymurus'' is an extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, alth ...

'' ;

Agnostida Agnostida is an order of arthropod which have classically been seen as a group of highly modified trilobites, though some recent research has doubted this placement. Regardless, they appear to be close relatives as part of the Artiopoda. They ar ...

of the Floian' *''

Galbagnostus ''Galbagnostus'' is an extinct genus of agnostid trilobite. It lived during the Lower and Middle Ordovician (Floian to Darriwillian). Distribution * ''G. galba'' has been found in the Middle Ordovician (Darriwillian) of Newfoundland, Canada ('' ...

'' *''

Geragnostella ''Geragnostus'' is a genus of very small agnostid trilobites whose fossils are found Ordovician-aged marine strata from Eurasia, North America and Argentina. Etymology * ''balanolobus'' is derived from the Greek 'balanos', acorn, and 'lob ...

'' ;

Asaphida Asaphida is a large, morphologically diverse order of trilobites found in marine strata dated from the Middle Cambrian until their extinction during the Silurian. Asaphida contains six superfamilies (Anomocaroidea, Asaphoidea, Cyclopygoidea, D ...

of the Floian Naturhistorisches Museum Vienna Dez 2006 073

*'' Phthanoncoceras'' *''

Ampyx In Greek mythology, Ampyx (Ancient Greek: Ἄμπυξ) or Ampycus (Ἄμπυκος ''Ampykos'' means 'woman's diadem, frontlet') was the name of the following figures: * Ampyx, also called Ampycus or AmpyceHesiod, ''Shield of Heracles'' 180 was a ...

'' *'' Ampyxoides'' *''

Anebolithus ''Anebolithus'' is a genus of trilobites found in Gilwern Hill, Powys, Wales Wales ( cy, Cymru ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by England to the Wales–England border, ...

'' *'' Asaphus'' *''

Aspidaeglina ''Aspidaeglina'' is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the early part of the Arenig stage of the Ordovician Period, a faunal stage which lasted from approximately 473 to 470 m ...

'' *''

Australopyge ''Australopyge'' is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the Arenig stage of the Ordovician Period The Ordovician ( ) is a geologic period and system, the second of six periods o ...

'' *'' Bergamia'' *'' Bohemopyge'' *''

Borogothus ''Borogothus'' is an extinct genus of trilobite arthropod. It lived during the Arenig stage of the Ordovician Period The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 ...

'' *''

Bumastides ''Bumastides'' is an extinct genus from a well-known class of fossil marine arthropods, the trilobite Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known ...

'' *'' Ceratolithus'' *''

Cloacaspis ''Cloacaspis'' is an extinct genus of Olenid Ptychopariid trilobite. It lived during the early part of the Arenig stage of the Ordovician Period, a faunal stage which lasted from approximately 478 to 471 million years ago. Richard Fortey ...

'' *''

Cnemidopyge ''Cnemidopyge'' is a genus of trilobites that lived during the Ordovician. Like all Raphiophorids it is blind, with a cephalon that is subtriangular to subsemicircular, carrying genal spines and a forward directed rapier-like spine on the central ...

'' *'' Degamella'' *'' Dionide'' *'' Dionidella'' *'' Ellipsotaphrus'' *''

Falanapis ''Falanapis'' is an extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, altho ...

'' *''

Famatinolithus ''Famatinolithus'' is an extinct genus from a well-known class of fossil marine arthropods, the trilobite Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-k ...

'' *''

Globampyx ''Globampyx'' is an extinct genus raphiophorid trilobites. It lived during the later part of the Arenig stage of the Ordovician Period, approximately 478 to 471 million years ago. Species of the genus are known from Canada (southeastern British ...

'' *''

Gog Gog may refer to: Religion * Gog and Magog, entities from various religious texts People * Anikó Góg, Hungarian triathlete * GOG or Genival Oliveira Gonçalves (born 1965), Brazilian rapper * Gog, a slang term for a person from North Wales ...

'' *'' Hanchungolithus'' *''

Hoekaspis ''Hoekaspis'' is an extinct genus of trilobites from the family Asaphidae.''Hoe ...

'' *'' Hungioides'' *'' Hunnebergia'' *'' Isocolus'' *'' Isoteloides'' *'' Lachnostoma'' *'' Lannacus'' *'' Lapidaria'' *'' Liomegalaspides'' *''

Megalaspidella ''Megalaspidella'' is an extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, ...

'' *''

Megalaspides ''Megalaspides'' is an extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, a ...

'' *''

Mendolaspis ''Mendolaspis'' is an extinct genus of trilobites. It lived during the Arenig stage of the Ordovician Period The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million ...

'' *''

Merlinia ''Merlinia'' is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the early part of the Arenig stage of the Ordovician Period, a faunal stage which lasted from approximately 478 to 471 mi ...

'' *'' Microparia'' *'' Mioptychopyge'' *''

Myttonia ''Myttonia'' is an extinct genus of trilobites in the family Trinucleidae Trinucleidae is a family of small to average size asaphida, asaphid trilobites that first occurred at the start of the Ordovician and became extinct at the end of that ...

'' *''

Ningkianolithus ''Ningkianolithus'' is an extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species ...

'' *''

Niobides In Greek mythology, the Niobids were the children of Amphion of Thebes, Greece, Thebes and Niobe, slain by Apollo and Artemis because Niobe, born of the royal house of Phrygia, had boastfully compared the greater number of her own offspring with t ...

'' *'' Ogmasaphus'' *''

Ogyginus ''Ogyginus'' is an extinct genus of asaphid trilobites that lived during the Ordovician period. Commonly found in Wales. The type specimen was first described by Murchison in 1839 as ''Asaphus corndensis'', though the species was later reassi ...

'' *'' Ogygiocaris'' *''

Opipeuter ''Proctoporus'' is a genus of medium-sized lizards ( snout-vent length between and ) assigned to the family Gymnophthalmidae. Species in the genus ''Proctoporus'' occur in Yungas forests and wet montane grasslands on the upper edge of t ...

'' *'' Parabasilicus'' *''

Paraptychopyge ''Paraptychopyge'' is an extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, ...

'' *'' Plesiomegalaspis'' *'' Presbynileus'' *''

Pricyclopyge ''Pricyclopyge'' is a genus of trilobites assigned to the family Cyclopygidae that occurs throughout the Ordovician. ''Pricyclopyge'' had aextratropical distribution, and there is evidence that it lived in darker parts of the water column (ar ...

'' *'' Psilacella'' *''

Psilocara ''Psilocara'' is an extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, alth ...

'' *'' Ptychopyge'' *'' Rhombampyx'' *'' Robergiella'' *'' Seleneceme'' *'' Stapeleyella'' *'' Taihungshania'' *''

Thysanopyge ''Thysanopyge'' is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived in what is now South America during the early part of the Arenig stage of the Ordovician Period, a faunal stage which lasted ...

'' *''

Trigonocercella ''Trigonocercella'' is an extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species ...

'' *''

Tungtzuella ''Tungtzuella'' is an extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, alt ...

'' *'' Zhenganites'' *''

Zuninaspis ''Zuninaspis'' is an extinct genus of trilobite arthropod. It lived during the Arenig stage of the Ordovician Period, approximately 478 to 471 million years ago in what is now Argentina.Corynexichida of the Floian *''

Bumastus ''Bumastus'' is an extinct genus of corynexochid trilobites which existed from the Early Ordovician period to the Late Silurian period. They were relatively large trilobites, reaching a length of . They were distinctive for their highly globular ...

'' *'' Dysplanus'' *''

Ectillaenus ''Ectillaenus'' is a genus of trilobites in the order Corynexochida. These nektobenthic carnivores lived in the Ordovician period, from 478.6 to 449.5 Ma. Taxonomy Species include: *''Ectillaenus advena'' (Barrande, 1872) *''Ectillaenus benigne ...

'' *''

Panderia ''Panderia'' is a genus of trilobites in the order Corynexochida Corynexochida is an order of trilobite that lived from the Lower Cambrian to the Late Devonian. Like many of the other trilobite orders, Corynexochida contains many species with ...

'' *'' Phillipsinella'' *'' Pseudocalymene'' *'' Theamataspis'' ;

Lichida Lichida is an order of typically spiny trilobite that lived from the Furongian to the Devonian period. These trilobites usually have 8–13 thoracic segments. Their exoskeletons often have a grainy texture or have wart or spine-like tubercles. ...

of the Floian *''

Apatolichas ''Apatolichas'' is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the later part of the Arenig stage of the Ordovician Period The Ordovician ( ) is a geologic period and system, the second ...

'' *'' Autoloxolichas'' *''

Lichakephalina ''Lichakephalina'' is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the Arenig, Arenig stage of the Ordovician Period, approximately 478 to 471 million years ago. References

Ordovic ...

'' *'' Metopolichas'' ;

Odontopleurida Odontopleurida is an order (biology), order of very spinose trilobites closely related to the trilobites of the order Lichida. Some experts group the Odontopleurid families, Odontopleuridae and Damesellidae, within Lichida. Odontopleurids tend ...

of the Floian *'' Phthanoncoceras'' *'' Ceratocephala'' *'' Diacanthaspis'' *'' Selenopeltis'' ;

Phacopida Phacopida ("lens-face") is an order of trilobites that lived from the Late Cambrian to the Late Devonian. It is made up of a morphologically diverse assemblage of taxa in three related suborders. Characteristics Phacopida had 8 to 19 thorac ...

of the Floian *''

Bathycheilus ''Bathycheilus'' is a genus of trilobites in the order Phacopida. It was described by Holub in 1908. Species * ''Bathycheilus castilianus'' Hammann, 1983 * ''Bathycheilus gallica'' Dean, 1965 * ''Bathycheilus galticus'' Dean, 1965 * ''Bathyche ...

'' *'' Calymenella'' *''

Ceraurinella ''Ceraurinella'' is an extinct genus of trilobite Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilo ...

'' *''

Colobinion ''Colobinion'' is an extinct genus of trilobite in the family Pliomeridae Pliomeridae is a family of phacopide trilobites, containing the following genera: *'' Anapliomera'' *'' Benedettia'' *'' Canningella'' *'' Colobinion'' *'' Coplacopa ...

'' *'' Colpocoryphe'' *''

Cybelopsis ''Cybelopsis'' is a trilobite in the order Phacopida, that existed during the lower Ordovician in what is now Greenland. It was described by Poulsen in 1927, and the type species is ''Cybelopsis speciosa''. The type locality for the genus w ...

'' *'' Cybelurus'' *''

Diaphanometopus ''Diaphanometopus'' is an extinct genus of trilobite in the order Phacopida. It is known from the Lower Ordovician of Russia (Oeland series, Pavlovsk). References External links ''Diaphanometopus''at the Paleobiology Database The Paleobi ...

'' *''

Dindymene Dindymene ( grc, Δινδυμήνη), in ancient Phrygian mythology, is one of the names of Cybele, mother of the gods. Temples to Dindymene were built in parts of ancient Ionia, such as Magnesia on the Maeander. The name may have been derived ...

'' *''

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