Cheiruridae is a family of

phacopid Phacopidae is a family of phacopid trilobites that ranges from the Lower Ordovician to the Upper Devonian, with representatives in all paleocontinents. Description As in all Phacopina, the eyes (if present) consist of very large (0.5 mm in ' ...

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 trilobites in the fossil record defines the base of the At ...

s of the suborder

Cheirurina Cheirurina is a suborder of the trilobite order Phacopida. Known representatives range from the uppermost Cambrian (upper Furongian) to the end of the Middle Devonian (Givetian The Givetian is one of two faunal stages in the Middle Devonian Pe ...

. Its members, as with other members of the suborder, had distinctive pygidia modified into finger-like spines. They first appeared in the uppermost

Cambrian The Cambrian Period ( ; sometimes symbolized C with bar, 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 ...

(upper

Furongian The Furongian is the fourth and final epoch and series of the Cambrian. It lasted from to million years ago. It succeeds the Miaolingian series of the Cambrian and precedes the Lower Ordovician Tremadocian Stage. It is subdivided into three sta ...

), and persisted until the end of the Middle

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

(

Givetian The Givetian is one of two faunal stages in the Middle Devonian Period. It lasted from million years ago to million years ago. It was preceded by the Eifelian Stage and followed by the Frasnian Stage. It is named after the town of Givet in Fra ...

). Currently about 657 species assigned to 99 genera are included.

Distribution

The subfamily Cheirurinae with 269 species in 38 genera occur from 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 lowe ...

to the Givetian and are probably

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...

. The 109 species in 15 genera of the Acanthoparyphinae are also probably monophyletic, and are known from the

to the

Ludfordian In the geologic timescale, the Ludfordian is the upper of two chronostratigraphic stages within the Ludlow Series. Its age is the late Silurian Period, and within both the Palaeozoic Era and Phanerozoic Eon. The rocks assigned to the Ludfordian ...

. The Cyrtometopinae were present between the Floian and the Upper

Katian The Katian is the second stage of the Upper Ordovician. It is preceded by the Sandbian and succeeded by the Hirnantian Stage. The Katian began million years ago and lasted for about 7.8 million years until the beginning of the Hirnantian millio ...

, enveloping 22 species in 5 genera, of which the monophyly is unclear. The Deiphoninae are probably monophyletic, occur from the

Dapingian The Dapingian is the third stage of the Ordovician period and the first stage of the Middle Ordovician series. It is preceded by the Floian and succeeded by the Darriwilian. The top of the Floian is defined as the first appearance of the conodont ...

to the

Gorstian In the geologic timescale, the Gorstian is an age of the Ludlow Epoch of the Silurian Period of the Paleozoic Era of the Phanerozoic Eon that is comprehended between 427.4 ± 0.5 Ma and 425.6 ± 0.9 Ma (million years ago), approximately. The Gor ...

, having 71 species assigned to 6 genera. The possibly

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

Eccoptochilinae with 67 species in 13 genera are known between the Floian and upper Katian. The Heliomerinae are a small monophyletic group with 13 species in 2 genera. The Pilekiinae are the earliest subfamilily and therefore certainly paraphyletic, occurring in the upper

and going extinct in the

Darriwilian The Darriwilian is the upper stage of the Middle Ordovician. It is preceded by the Dapingian and succeeded by the Upper Ordovician Sandbian Stage. The lower boundary of the Darriwilian is defined as the first appearance of the graptolite species '' ...

with 56 known species assigned to 19 genera. The

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

Sphaerexochinae has about 50 species between the Floian and Přídolí.

Genera

*'' Acanthoparypha'' *'' Actinopeltis'' *'' Anasobella'' *'' Ancyginaspis'' *'' Apollonaspis'' *'' Arcticeraurinella'' *'' Areia'' *'' Areiaspis'' *'' Azyptyx'' *'' Barrandeopeltis'' *'' Borealaspis'' *'' Bornholmaspis'' *'' Bufoceraurus'' *'' Ceraurinella'' *'' Ceraurinium'' *'' Ceraurinus'' *'' Cerauromeros'' *'' Cerauropeltis'' *''

Ceraurus ''Ceraurus'' is a genus of cheirurid trilobite of the middle and, much more rarely, the upper Ordovician. They are commonly found in strata of the lower Great Lakes region. These trilobites have eleven thoracic segments, a very small pygidium a ...

'' *''

Cheirurus ''Cheirurus'' (from Greek ''χείρ, cheir'' meaning "hand" and ''ουρά, oura'' meaning "tail") is a genus of phacopid trilobites that lived from the Ordovician to the Devonian. Its remains have been found in Africa, Asia, Australia, Euro ...

'' (

type genus In biological taxonomy, the type genus is the genus which defines a biological family and the root of the family name. Zoological nomenclature According to the International Code of Zoological Nomenclature, "The name-bearing type of a nominal f ...

) *'' Chiozoon'' *'' Contracheirurus'' *'' Courtessolium'' *'' Crotalocephalides'' *'' Crotalocephalina'' *''

Crotalocephalus ''Crotalocephalus'' is a genus of trilobites that lived from the Late Silurian to the Early Devonian. Its remains have been found in Asia, Australia, Africa, and Europe. References External links ''Crotalocephalus''in the Paleobiology Data ...

'' *'' Cybelloides'' *'' Cyrtometopus'' *''

Deiphon ''Deiphon'' is a distinctive genus of Silurian phacopid trilobites of the family Cheiruridae found in Western and Central Europe, and in Central and Eastern United States. The type species, ''D. forbesi'', from England, Bohemia, and Sweden, was ...

'' *'' Didrepanon'' *'' Eccoptochile'' *'' Eccoptochiloides'' *'' Forteyops'' *'' Foulonia'' *'' Gabriceraurus'' *'' Geracephalina'' *'' Hadromeros'' *'' Hammannopyge'' *'' Hapsiceraurus'' *'' Heliomera'' *'' Heliomeroides'' *'' Holia'' *'' Hyrokybe'' *'' Junggarella'' *'' Kawina'' *'' Kolymella'' *'' Krattaspis'' *'' Ktenoura'' *'' Laneites'' *''

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 islands ...

'' *'' Leviceraurus'' *'' Nieszkowskia'' *'' Onycopyge'' *'' Osekaspis'' *'' Pandaspinapyga'' *'' Paraceraurus'' *'' Parasphaerexochus'' *'' Parayoungia'' *'' Parisoceraurus'' *'' Pateraspis'' *'' Patomaspis'' *'' Placoparina'' *'' Pompeckia'' *'' Proromma'' *'' Protocerauroides'' *'' Pseudocheirurus'' *'' Pseudosphaerexochus'' *'' Radiurus'' *'' Ratinkaspis'' *'' Reraspis'' *'' Skelipyx'' *'' Sphaerexochus'' *'' Sphaerocoryphe'' *'' Stubblefieldia'' *'' Sycophantia'' *'' Turantyx'' *'' Valongia'' *'' Whittakerites'' *'' Xylabion'' *'' Xystocrania'' *''

Youngia ''Youngia'' is a genus of Asian plants in the tribe Cichorieae within the family Asteraceae. There are several weedy species in the genus as well as the endangered ''Youngia nilgiriensis'' from Sispara in southern India, and '' Youngia japonica' ...

'' *'' Zazvorkaspis''

References

External links

* Trilobite families Cambrian trilobites Ordovician trilobites Silurian trilobites Devonian trilobites Furongian first appearances Givetian extinctions Paleozoic life of Newfoundland and Labrador {{phacopida-stub