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

, the Arenig (or Arenigian) is a time interval during the

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 ...

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 ...

in 1847 with reference to the "Arenig Ashes and Porphyries" in the neighbourhood of

Arenig Fawr Arenig Fawr ( en, Great High Ground) is a mountain in Snowdonia, North Wales, close to Llyn Celyn reservoir, alongside the A4212 between Trawsfynydd and Bala. Location Arenig Fawr is the highest member of the Arenig range, with Arenig F ...

, in

Merioneth , HQ= Dolgellau , Government= Merionethshire County Council (1889-1974) , Origin= , Status= , Start= 1284 , End= , Code= MER , CodeName= ...

North Wales North Wales ( cy, Gogledd Cymru) is a regions of Wales, region of Wales, encompassing its northernmost areas. It borders Mid Wales to the south, England to the east, and the Irish Sea to the north and west. The area is highly mountainous and rural, ...

. 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 Llandeilo () is a town and community in Carmarthenshire, Wales, situated at the crossing of the River Towy by the A483 on a 19th-century stone bridge. Its population was 1,795 at the 2011 Census. It is adjacent to the westernmost point of the ...

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 Mehedin� ...

Caradoc Caradoc Vreichvras (; Modern cy, Caradog Freichfras, ) was a semi-legendary ancestor to the kings of Gwent. He may have lived during the 5th or 6th century. He is remembered in the Matter of Britain as a Knight of the Round Table, under the ...

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 ago ...

rocks; this is not the case in South Wales. The Arenig series is represented in North Wales by the Garth Grit and Ty Obry beds, by the Shelve series of the Corndon district, the Skiddaw Slates of the Lake District, the Ballantrae Group of

Ayrshire Ayrshire ( gd, Siorrachd Inbhir Àir, ) is a 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 and it borders the counties of ...

, and by the Ribband Series of slates and shale in Wicklow 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/N11 ...

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

, 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 of the ICS, 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 ( 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. Th ...

Whiterockian The Whiterockian, often referred to simply as the Whiterock, is an earliest or lowermost stage of the Middle Ordovician. Although the Whiterockian or Whiterock Stage refers mainly to the early Middle Ordovician in North America, it is often used in ...

which is the lower part of the now shortened

Chazyan The Chazy Reef Formation is a mid-Ordovician limestone deposit in northeastern North America. It consists of some of the oldest reef systems built by a community of organisms rather than the deposit of a limited range of similar organisms, such ...

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, w ...

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 sup ...

of the Floian *''Acanthambonia'' *'' Cyrbasiotreta'' *''Eoconulus'' *''Issedonia'' *'' Karnotreta'' *'' Lurgiticoma'' *'' Multispinula'' *'' Mylloconotreta'' *''Numericoma'' *''Orthisocrania'' *''Polylasma'' *'' Pomeraniotreta'' *''Pseudocrania'' *'' Scaphelasma'' *''Schizotreta'' *''Torynelasma'' ;

Lingulida Lingulida is an order of 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. Brachiopo ...

of the Floian *''Acanthorthis'' *''Aulonotreta'' *''Dictyobolus'' *''Ectenoglossa'' *'' Elliptoglossa'' *'' Monobolina'' *''Paldiskites'' *'' Paterula'' *'' Pseudolingula'' *'' Quasithambonia'' *'' Rafanoglossa'' *''Volborthia'' ;

Orthida Orthida is an extinct order of brachiopods which appeared during the Early Cambrian period and became very diverse by the Ordovician, living in shallow-shelf seas. Orthids are the oldest member of the subphylum Rhynchonelliformea, and is the or ...

of the Floian *'' Acanthorthis'' *'' Acanthotoechia'' *'' Anchigonites'' *'' Angusticardinia'' *'' Anomalorthis'' *'' Antigonambonites'' *'' Apomatella'' *'' Astraborthis'' *'' Crossiskenidium'' *''Dalmanella'' *'' Desmorthis'' *''Diparelasma'' *'' Eodiorthelasma'' *''Eosotrematorthis'' *'' Estlandia'' *'' Euorthisina'' *'' Famatinorthis'' *'' Fasciculina'' *'' Ferrax'' *'' Ffynnonia'' *'' Fistulogonites'' *'' Glossorthis'' *''Glypterina'' *'' Hesperonomiella'' *'' Incorthis'' *'' Jaanussonites'' *'' Ladogiella'' *''Lomatorthis'' *'' Monorthis'' *'' Munhella'' *'' Nereidella'' *'' Neumania'' *'' Nocturneilla'' *'' Notoscaphidia'' *'' Oligorthis'' *'' Orthambonites'' *'' Orthidiella'' *'' Orthidium'' *'' Orthis'' *'' Oslogonites'' *'' Panderina'' *'' Paralenorthis'' *'' Paurorthina'' *'' Paurorthis'' *'' Phragmorthis'' *'' Platystrophia'' *'' 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, and ...

'' *'' Treioria'' *'' Trematorthis'' *'' Valcourea'' *'' Virgoria'' ; Paternida of the Floian *'' Dictyonites'' ;

Pentamerida Pentamerida is an order of biconvex, impunctate shelled, articulate brachiopods that are found in marine sedimentary rocks that range from the Middle Cambrian through the Devonian.Moore, Lalcker and Fischer, 1952, Invertebrate Fossils, McGraw-Hil ...

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 Esto ...

'' *'' Leptestia'' *'' Petroria'' *'' Plectambonites'' *'' Reinversella'' *'' Schedophyla'' *''Taffia'' *'' Tourmakeadia'' ;

Trimerellida Trimerellida is an extinct order of craniate brachiopods, containing the superfamily Trimerelloidea and the families Adensuidae, Trimerellidae, and Ussuniidae. Trimerellidae is a small but widespread family of warm-water brachiopods ranging ...

of the Floian *'' Dinobolus''

Cephalopoda

; Actinocerida *'' Metactinoceras'' *'' Ordosoceras'' *'' Polydesmia''

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'' *'' Nybyoceras'' *'' Actinoceras'' *'' Wutinoceras'' *'' Ormoceras'' *'' Adamsoceras'' *''Georgina''

Orthocerida

; Orthocerids of the Floian *'' Eobactrites'' ; Barrandeocerida of the Floian *'' Plectoceras'' ;

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 ar ...

of the Floian *'' Amsleroceras'' *'' Apocrinoceras'' *'' Avoceras'' *'' Bakeroceras'' *'' Baltoceras'' *'' Catoraphinoceras'' *'' Cochlioceras'' *'' Copiceras'' *'' Clelandoceras'' *'' Cumberloceras'' *'' Cyclostomiceras'' *'' Cyrtobaltoceras'' *'' Desioceras'' *'' Diaphoroceras'' *'' Diastoloceras'' *'' Dwightoceras'' *'' Dyscritoceras'' *'' Ectocycloceras'' *'' Endorioceras'' *'' Eocyckistomiceras'' *'' Eothinoceras'' *'' Hemichoanella'' *'' Irianoceras'' *'' Kyminoceras'' *'' Lawrenceoceras'' *'' Meikeloceras'' *'' Microbaltoceras'' *'' Monogonoceras'' *'' Ogygoceras'' *'' Pictetoceras'' *'' Protocycloceras'' *'' Quebecoceras'' *'' Rangeroceras'' *'' Rhabdiferous'' *'' Rioceras'' *'' Rudolfoceras'' *'' Smithvilloceras'' *'' Somalinautilus'' *'' Somalinautilus'' *'' Somalinautilus'' *'' Vassaroceras'' *'' Veneficoceras'' *'' 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'' *'' Dartonoceras'' *'' Kaipingoceras'' *'' Kugeloceras'' *'' Lobosiphon'' *'' Manitouoceras'' *'' Mcqueenoceras'' *'' Mysticoceras'' *'' Notocycloceras'' *'' Oderoceras'' *'' Parapiloceras'' *'' Phragmosiphon'' *'' Platysiphon'' *'' Pliendoceras'' *'' Retroclitendoceras'' *'' Stenosiphon'' *'' 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'' *'' 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 slig ...

'' *'' Proterovaginoceras'' *'' Cyrtendoceras'' *'' Anthoceras'' *'' Chaohuceras'' *'' Proterocameroceras'' *'' 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'' *'' Chihlioceras'' *'' Cyclocyrtendoceras'' *'' Cyptendoceras'' *'' Kirkoceras'' *'' Lobendoceras'' *'' 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 of the Floian *'' Phthanoncoceras'' *'' Valhalloceras'' ; Nautiloids of the Floian *'' Buttsoceras'' *'' Centroonoceras'' *'' Gangshanoceras'' *'' Geisonoceras'' *''

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 ...

'' *'' Orthoceras'' *'' Oxfordoceras'' *'' Rhynchorthoceras'' *'' Stereoplasmoceras'' *'' Tajaroceras'' *'' Wardoceras'' ; Tarphycerida *'' Deltoceras'' *'' Pseudancistroceras'' *'' Seelyoceras'' ;Lower *''

Alaskoceras ''Alaskoceras'' is a genus of lower Ordovician coiled nautiloid cephalopods; the shell moderately expanded, ribbed, with a divergent living chamber; whorl section more broadly rounded ventrally than dorsally; siphuncle marginal at maturity, septa ...

'' *'' Moreauoceras'' *'' Pilotoceras'' *'' Shumardoceras'' *'' Pycnoceras'' *'' Campbelloceras'' *''

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'' *'' Bentoceras'' *'' Centrotarphyceras'' *'' Clytoceras'' *'' Cycloplectoceras'' *'' Eichwaldoceras'' *'' Eurystomites'' *'' Hardmanoceras'' *'' Holmiceras'' *'' 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 t ...

'' *'' Litoceras'' *'' Curtoceras'' *'' 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''

Trilobite fauna

;Trilobites of the Floian *'' Canningella'' *'' Gogoella'' *'' Macrogrammus'' *'' Priceaspis'' *'' Thymurus'' ;

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 a ...

of the Floian' *'' Galbagnostus'' *'' Geragnostella'' ;

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, ...

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 ...

'' *'' Ampyxoides'' *'' Anebolithus'' *''

Asaphus ''Asaphus'' () is a genus of trilobites that is known from the Lower (upper Arenig) and Middle Ordovician of northwestern Europe (Sweden, Estonia, Saint Petersburg Area). Etymology The generic name is derived from the Greek word ''asaphes'', ...

'' *'' Aspidaeglina'' *'' Australopyge'' *'' Bergamia'' *'' Bohemopyge'' *'' Borogothus'' *'' Bumastides'' *''

Ceratolithus ''Ceratolithus'' 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, approximately 478 to 471 million years ago. Distribution '' ...

'' *'' Cloacaspis'' *'' Cnemidopyge'' *'' Degamella'' *'' Dionide'' *'' Dionidella'' *'' Ellipsotaphrus'' *'' Falanapis'' *'' Famatinolithus'' *'' Globampyx'' *'' Gog'' *'' Hanchungolithus'' *'' Hoekaspis'' *'' Hungioides'' *'' Hunnebergia'' *'' Isocolus'' *'' Isoteloides'' *''

Lachnostoma ''Lachnostoma'' 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 In chronostratigraphy, a stage is a successi ...

'' *'' Lannacus'' *'' Lapidaria'' *'' Liomegalaspides'' *'' Megalaspidella'' *'' Megalaspides'' *'' Mendolaspis'' *'' Merlinia'' *'' Microparia'' *'' Mioptychopyge'' *'' Myttonia'' *'' Ningkianolithus'' *'' Niobides'' *'' Ogmasaphus'' *'' Ogyginus'' *'' Ogygiocaris'' *'' Opipeuter'' *'' Parabasilicus'' *'' Paraptychopyge'' *'' Plesiomegalaspis'' *'' Presbynileus'' *'' Pricyclopyge'' *'' Psilacella'' *'' Psilocara'' *'' Ptychopyge'' *'' Rhombampyx'' *'' Robergiella'' *'' Seleneceme'' *'' Stapeleyella'' *'' Taihungshania'' *'' Thysanopyge'' *'' Trigonocercella'' *'' Tungtzuella'' *'' Zhenganites'' *'' Zuninaspis'' ; 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'' *'' Panderia'' *'' 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. So ...

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 se ...

'' *'' Autoloxolichas'' *'' Lichakephalina'' *'' Metopolichas'' ;

Odontopleurida Odontopleurida is an 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 to have convex, ...

of the Floian *'' Phthanoncoceras'' *'' Ceratocephala'' *'' Diacanthaspis'' *'' Selenopeltis'' ; Phacopida of the Floian *'' Bathycheilus'' *'' Calymenella'' *'' Ceraurinella'' *'' Colobinion'' *''

Colpocoryphe ''Colpocoryphe'' is a genus of trilobites in the family Calymenidae. Morphology * Convex Cephalon Cephalon, Inc. was an American biopharmaceutical company co-founded in 1987 by pharmacologist Frank Baldino, Jr., neuroscientist Michael Lew ...

'' *'' Cybelopsis'' *'' Cybelurus'' *'' Diaphanometopus'' *''

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 derive ...

'' *'' Eccoptochile'' *'' Ectenonotus'' *'' Encrinurella'' *'' Encrinuroides'' *'' Evropeites'' *''

Gyrometopus ''Gyrometopus'' 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, approximately 479 to 472 million years ago. Description The central raised ar ...

'' *'' Heliomeroides'' *'' Kanoshia'' *'' Kawina'' *'' Kolymella'' *''

Lehua Lehua Island is a small, crescent-shaped island in the Hawaiian islands, north of Niihau, due west of Kauai. The uninhabited, barren island is a tuff cone which is part of the active Niihau volcano. Lehua was one of the first five isl ...

'' *'' Lyrapyge'' *'' Neseuretus'' *'' Nieszkowskia'' *'' Ormathops'' *'' Ovalocephalus'' *'' Placoparia'' *'' Platycoryphe'' *'' Pliomeridius'' *'' Pliomerops'' *'' Protoencrinurella'' *'' Protopliomerella'' *'' Pseudocybele'' *'' Pterygometopus'' *'' Strotactinus'' *'' Sycophantia'' *'' Synhomalonotus'' *'' Toletanaspis'' *'' Xystocrania'' ; Proetida of the Floian *'' Acidiphorus'' *'' Bathyuriscops'' *'' Benthamaspis'' *'' Biolgina'' *'' Bolbocephalus'' *''

Carolinites ''Carolinites'' is a genus of trilobite, assigned to the Telephinidae family, that occurs during the Lower and Middle Ordovician. ''Carolinites'' had a pantropical distribution, and there is evidence that it lived in upper parts of the water co ...

'' *'' Celmus'' *'' Ceratopeltis'' *'' Decoroproetus'' *'' Dimeropygiella'' *'' Eleutherocentrus'' *'' Goniophrys'' *'' Goniotelina'' *'' Grinnellaspis'' *'' Ischyrophyma'' *'' Ischyrotoma'' *'' Lutesvillia'' *'' Oenonella'' *'' Petigurus'' *'' Rananasus'' *'' Raymondaspis'' *'' Telephina'' ; Ptychopariida of the Floian *''

Anaximander Anaximander (; grc-gre, Ἀναξίμανδρος ''Anaximandros''; ) was a pre-Socratic Greek philosopher who lived in Miletus,"Anaximander" in ''Chambers's Encyclopædia''. London: George Newnes, 1961, Vol. 1, p. 403. a city of Ionia (in mo ...

'' *'' Annamitella'' *'' Balnibarbi'' *'' Bulnibarbi'' *'' Bvalbardites'' *'' Circulocrania'' *'' Endymionia'' *'' Etheridgaspis'' *'' Furcalithus'' *'' Gymnostomix'' *'' Lacorsalina'' *'' Leioshumardia'' *'' Lordshillia'' *'' Nambeetella'' *'' Novakella'' *'' Oopsites'' *'' Peraspis'' *'' Phorocephala'' *'' Porterfieldia'' *'' Prosopiscus'' *'' Pytine'' *'' Sagavia'' *'' Selenoharpes'' *'' Stegnopsis'' *'' Stenorhachis'' *'' Svalbardites'' *'' Tasmanocephalus'' *'' Turgicephalus'' *'' Yinpanolithus''

External links

palaeos

References

{{Reflist Early Ordovician