Raphiophoridae is a family of small to average-sized

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 that first occurred at the start of the

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

and became extinct at the end of the Middle

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...

Anatomy

All raphiophorids are blind, with headshields (or cephalons) that are triangular to subcircular, and many carry long, trailing genal spines, a forward-directed rapier-like spine on the central raised area (or

glabella The glabella, in humans, is the area of skin between the eyebrows and above the nose. The term also refers to the underlying bone that is slightly depressed, and joins the two brow ridges. It is a cephalometric landmark that is just superior to ...

), or both, with the glabella often inflated and the natural fracture lines (or sutures) of the cephalon coinciding with its margin. The thorax typically has five to seven segments (except for the genera ''Taklamakania'', ''Pseudampyxina'', ''Nanshanaspis'', and ''Kongqiangheia'', which have only 3). As mentioned before, all raphiophorids are blind. Many, if not most, genera have no eyes whatsoever, though a few, such as '' Lehnertia'', have vestigial tubercles that correspond to the compound eyes of their ancestors.

Distribution

Raphiophoridae currently includes two officially recognized subfamilies. The nominal subfamily Raphiophorinae originated from the Upper

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 ...

and died out during the Lower

Ludlow Ludlow () is a market town in Shropshire, England. The town is significant in the history of the Welsh Marches and in relation to Wales. It is located south of Shrewsbury and north of Hereford, on the A49 road which bypasses the town. The t ...

, and has 217 species assigned to it divided over 26 genera. The subfamily Endymioniinae occurred 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 ...

or possibly from the Lower Tremadocian to 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 million ...

and contains 36 species in 13 genera. The time of the first occurrence depends on whether the inadequately known monotypic genus ''Typhlokorynetes'' from the Lower Tremadocian of

Laurentia Laurentia or the North American Craton is a large continental craton that forms the ancient geological core of North America. Many times in its past, Laurentia has been a separate continent, as it is now in the form of North America, although ...

is considered an endymioniin. Raphiophorids are generally found in deep-water sediments, and have a cosmopolitan distribution from the Floian to the

Ordovician–Silurian extinction events The Late Ordovician mass extinction (LOME), sometimes known as the end-Ordovician mass extinction or the Ordovician-Silurian extinction, is the first of the "big five" major Extinction event, mass extinction events in Earth's history, occurring ro ...

with diversity peaking from 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 '' ...

to the

Sandbian The Sandbian is the first stage of the Upper Ordovician. It follows the Darriwilian and is succeeded by the Katian. Its lower boundary is defined as the first appearance datum of the graptolite species '' Nemagraptus gracilis'' around million yea ...

. ''Raphiophorus'' survived into the Silurian.

Taxonomy

The subfamily Taklamakaniinae was erected to bring together the genera ''Nanshanaspis'', ''Pseudampyxina'', and ''Taklamakania'', (and then, later, ''Kongqiangheia'') on the basis that they all have only three thoracic segments. Analysis of adult anatomy of these genera and larval stages of other raphiophorids showed they most probably developed through

paedomorphosis Neoteny (), also called juvenilization,Montagu, A. (1989). Growing Young. Bergin & Garvey: CT. is the delaying or slowing of the physiological, or somatic, development of an organism, typically an animal. Neoteny is found in modern humans compared ...

from three different ancestors, so provide an example of

parallel evolution Parallel evolution is the similar development of a trait in distinct species that are not closely related, but share a similar original trait in response to similar evolutionary pressure.Zhang, J. and Kumar, S. 1997Detection of convergent and paral ...

. ''Nanshanaspis'' closely resembles young ''Globampyx'', ''Pseudampyxina'' strongly looks like juvenile ''Raymondella'', and ''Taklamakania'' is almost identical to early stages of ''Ampyxina''. Since the three genera of the Taklamakaniinae have been demonstrated to be unrelated to each other, this subfamily is regarded as

polyphyletic A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of converg ...

, and has been synonymized with the Raphiophorinae.

Genera

These genera are assigned to the Raphiophoridae:
Subfamily Raphiophorinae * '' Raphiophorus'' Angelin, 1854 * ''

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 ...

'' Dalman, 1827 * '' Ampyxella'' Dean, 1960 * '' Ampyxina'' Ulrich, 1922 * '' Ampyxoides'' Whittington, 1965 * '' Bulbaspis'' Chugaeva, 1956 * '' Cnemidopyge'' Whittard, 1955 * '' Edmundsonia'' Cooper, 1953 * '' Globampyx'' Fortey, 1975 * ''

Kongqiangheia ''Kongqiaoheia rotundata'' is an asaphid trilobites of the family Raphiophoridae that lived during the late Caradoc of Inner Mongolia, China. ''K. rotundata'' was originally grouped with the so-called Taklamakaniinae, a paraphyletic group of ti ...

'' * ''

Lonchodomas ''Lonchodomas'' is a genus of trilobites, that lived during the Ordovician. It was eyeless, like all raphiophorids, and had a long straight sword-like frontal spine, that gradually transforms into the relatively long glabella. Both the glabellar ...

'' Angelin, 1854 * '' Mendolaspis'' Rusconi, 1951 * ''

Nanshanaspis ''Nanshanaspis'' is a genus of asaphid trilobites of the family Raphiophoridae that lived during the late Caradoc of Inner Mongolia, China. Like all raphiophorids it is blind, with a headshield (or cephalon) that is subsemicircular, carrying gen ...

'' Chang & Fan, 1960 * '' Pseudampyxina'' Ju, 1983 * '' Raymondella'' Reed, 1935 * '' Rhombampyx'' Fortey, 1975 * ''

Taklamakania ''Taklamakania'' is a genus of asaphid trilobites of the family Raphiophoridae that lived during the late Caradoc of Inner Mongolia, China. Like all raphiophorids it is blind, with a headshield (or cephalon) that is subsemicircular, carrying ge ...

'' Zhang, 1980 Subfamily Endymioniinae * '' Endymionia'' Billings, 1865 * '' Ampyxinella'' Koroleva, 1959 * '' Ampyxinops'' Zhang 1979 * '' Anisonotella'' Whittington, 1965 * '' Carinocranium'' Dean, 1989 * '' Edmundsonia'' Cooper 1953 * '' Jiuxiella'' Zhou et al. 1977 * '' Lehnertia'' Vaccari, et al, 2006 * '' Malongullia'' Webby, Moors & McLean, 1970 * '' Miaopopsis'' Lu et al. 1965, synonym = ''Sinampyxina'' * '' Miboshania'' Zhang 1979 * ''

Pytine ''Pytine'' is an extinct genus of asaphida, asaphid trilobites. Species lived during the later part of the Arenig, Arenig stage of the Ordovician Period, approximately 478 to 471 million years ago. Various species are found in the Svalbard, Val ...

'' Fortey, 1975 * '' Salteria'' Thomson, 1864 *? '' Tarimella'' W. T. Zhang 1979 (may be a shumardiid ptychopariid) * '' Typhlokorynetes'' Shaw, 1966

References

{{Taxonbar, from=Q1245960 Trinucleioidea Trilobite families Ordovician trilobites Silurian trilobites Early Ordovician first appearances Silurian extinctions