Siphonotretida is an extinct

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

linguliform Linguliformea is a subphylum of inarticulate brachiopods. These were the earliest of brachiopods, ranging from the Cambrian into the Holocene. They rapidly diversified during the Cambrian into the Ordovician, but most families became extinct by ...

brachiopod Brachiopods (), phylum (biology), phylum Brachiopoda, are a phylum of 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 e ...

s in the

class Class, Classes, or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used d ...

Lingulata Lingulata is a class of brachiopods, among the oldest of all brachiopods having existed since the Cambrian period (). They are also among the most morphologically conservative of the brachiopods, having lasted from their earliest appearance to the ...

. The order is equivalent to the sole superfamily Siphonotretoidea, itself containing the sole family Siphonotretidae. Siphonotretoids were originally named as a superfamily of

Acrotretida Acrotretides (Acrotretida) are an extinct order of linguliform brachiopods in the class Lingulata. Acrotretida contains 8 families within the sole superfamily Acrotretoidea. They lived from the Lower Cambrian to the Middle Devonian, rapidly div ...

, before being raised to their own order.

Evolution

Spihonotretids were most abundant in the

late Cambrian The Furongian is the fourth and final Epoch (geology), epoch and Series (stratigraphy), series of the Cambrian. It lasted from to million years ago. It succeeds the Miaolingian series of the Cambrian and precedes the Lower Ordovician Tremadocia ...

and

Early Ordovician The Early Ordovician is the first epoch (geology), epoch of the Ordovician period, corresponding to the Lower Ordovician series (stratigraphy), series of the Ordovician system. It began after the Cambrian Stage 10, Age 10 of the Furongian epoch o ...

(

Furongian The Furongian is the fourth and final epoch and series of the Cambrian The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding ...

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

), and were traditionally considered to have gone extinct in the

Upper Ordovician The Late Ordovician is the third and final epoch of the Ordovician period, lasting million years and spanning from around 458.2 to 443.1 million years ago. The rocks associated with this epoch are referred to as the Upper Ordovician Series. At ...

Ashgill Ashgill is a village in South Lanarkshire, Scotland near Larkhall. It is part of the Dalserf parish. The village church dates back to 1889. It is twinned with Saint-Cirq-Lapopie in France. The village has a shop, a chip shop and a hairdress ...

"). More recently, new siphonotretids have been described as early as

Cambrian Stage 4 Cambrian Stage 4 is the still unnamed fourth stage of the Cambrian and the upper stage of Cambrian Series 2. It follows Cambrian Stage 3 and lies below the Wuliuan. The lower boundary has not been formally defined by the International Commission o ...

('' Schizambon'') and as late as the

Ludlow Ludlow ( ) is a market town and civil parish in Shropshire (district), Shropshire, England. It is located south of Shrewsbury and north of Hereford, on the A49 road (Great Britain), A49 road which bypasses the town. The town is near the conf ...

Epoch of the

Silurian The Silurian ( ) is a geologic period and system spanning 23.5 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 third and shortest period of t ...

('' Orbaspina''). Isolated fragments are even known from the

Emsian The Emsian is one of three faunal stages in the Early Devonian Epoch. It lasted from 410.62 ±1.95 million years ago to 393.47 ±0.99 million years ago. It was preceded by the Pragian Stage and followed by the Eifelian Stage. It is named after ...

stage of the

Lower Devonian The Early Devonian is the first of three epochs comprising the Devonian period, corresponding to the Lower Devonian series. It lasted from and began with the Lochkovian Stage , which was followed by the Pragian from and then by the Emsian, whic ...

. Archaic Cambrian-style siphonotretids such as ''Schizambon'' and '' Helmersenia'', with basic forms of ornamentation, populated the shores of

Baltica Baltica is a paleocontinent that formed in the Paleoproterozoic and now constitutes northwestern Eurasia, or Europe north of the Trans-European Suture Zone and west of the Ural Mountains. The thick core of Baltica, the East European Craton, i ...

Laurentia Laurentia or the North American craton is a large continental craton that forms the Geology of North America, 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 ...

, and

Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...

by the start of the Ordovician. In the late

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 datum ...

, advanced Ordovician-style spiny siphonotretids spread out from

temperate In geography, the temperate climates of Earth occur in the middle latitudes (approximately 23.5° to 66.5° N/S of the Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ran ...

waters around Gondwana and mostly replaced their older relatives.

Anatomy

Siphonotretids had simple, rounded shells, with an ornamentation of hollow spines or rarely pointed tubercles. The shell is usually ventribiconvex (both valves convex, the ventral valve moreso) and composed of microscopic granules of

apatite Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of Hydroxide, OH−, Fluoride, F− and Chloride, Cl− ion, respectively, in the crystal. The formula of the admixture of ...

. The inner surface of the shell tends to be weakly mineralized, so many aspects of the musculature and other soft anatomy are difficult to estimate in most species. Available data supports comparison to the internal structures of lingulids. Siphonotretids may be related to the linguloid families Lingulellotretidae or Dysoristidae. Similar to acrotretides, the pedicle foramen was set at the apex of the ventral valve, though it is often elongated into a tubular groove opening forwards. This groove lies on a triangular extension of the ventral valve, known as a pseudointerarea, which overhangs the dorsal valve. Unlike acrotretides, the adult shell is spinose while the larval shell lacks a pitted texture. The possible siphonotretid '' Acanthotretella'' is known from several exceptionally-preserved specimens which reveal lingulid-like traits such as

seta In biology, setae (; seta ; ) are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Depending partly on their form and function, protostome setae may be called macrotrichia, chaetae, ...

e, a spirolophous

lophophore The lophophore () is a characteristic feeding organ possessed by four major groups of animals: the Brachiopoda, Bryozoa, Hyolitha, and Phoronida, which collectively constitute the protostome group Lophophorata.epibenthic Benthos (), also known as benthon, is the community of organisms that live on, in, or near the bottom of a sea, river, lake, or stream, also known as the benthic zone.infaunal Fauna (: faunae or faunas) is all of the animal life present in a particular region or time. The corresponding terms for plants and fungi are ''flora'' and ''funga'', respectively. Flora, fauna, funga and other forms of life are collectively r ...

(burrowing) lingulids.

List of genera

* '' Acanthambonia'' Cooper, 1956 (

Ordovician The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era, and the second of twelve periods of the Phanerozoic Eon (geology), Eon. The Ordovician spans 41.6 million years f ...

, "

Arenig In geology, 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 in 1847 with reference to the "Areni ...

" to "

") * '' Acanthotretella?'' Holmer & Caron, 2006 (mid-Cambrian, "

Stage 4 Stage 4 may refer to: * Key Stage 4 * ''Stage 4'' of ''Everywhere at the End of Time'' * Cambrian Stage 4 Cambrian Stage 4 is the still unnamed fourth stage of the Cambrian and the upper stage of Cambrian Series 2. It follows Cambrian Stage 3 an ...

" to

Miaolingian The Miaolingian is the third Series of the Cambrian Period, and was formally named in 2018. It lasted from about to million years ago and is divided in ascending order into 3 stages: the Wuliuan, Drumian, and Guzhangian. The Miaolingian is prec ...

; provisionally assigned to Siphonotretoidea) * '' Alichovia'' Goryanskij, 1969 (Ordovician, " Tremadoc" to "

Caradoc Caradoc Vreichvras (; Modern , ) 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 names King Carados and C ...

") * '' Collarotrella'' Mergl, 1997 (Ordovician, "Arenig") * '' Celdobolus'' Havlíček, 1982 (Ordovician, "Arenig") * '' Cyrbasiotreta'' Williams & Curry, 1985 (Middle Ordovician, "Arenig") * '' Eosiphonotreta'' Havlíček, 1982 (Lower to Middle Ordovician, "Arenig" to "

Llanvirn The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era, and the second of twelve periods of the Phanerozoic Eon. The Ordovician spans 41.6 million years from the end of the Cambrian Period Ma (millio ...

") * '' Gorchakovia'' Popov & Khazanovitch (in Popov et al., 1989) (Upper Cambrian) * '' Helmersenia'' Pander (in von Helmersen, 1861) (Upper Cambrian to Ordovician) * '' Karnotreta'' Williams & Curry, 1985 (Middle Ordovician, "Arenig") * '' Mesotreta'' Kutorga, 1848 (Lower to Middle Ordovician, "Arenig") * '' Multispinula'' Rowell, 1962 (Middle to Upper Ordovician, "Arenig" to "Ashgill") * '' Nushbiella'' Popov (in Kolobova & Popov, 1986) (Middle to Upper Ordovician, "Arenig" to "Caradoc") * '' Oaxaquiatreta'' Streng, Mellbin, Landing & Keppie, 2011 (Upper Cambrian to

) * '' Orbaspina'' Valentine & Brock, 2003 (

, late

Llandovery Llandovery (; ) is a market town and community (Wales), community in Carmarthenshire, Wales. It lies on the River Tywi and at the junction of the A40 road, A40 and A483 road, A483 roads, about north-east of Carmarthen, north of Swansea and w ...

) * '' Quasithambonia?'' Bednarczyk & Biernat, 1978 (Ordovician, "Arenig") * '' Schizambon'' Walcott, 1884 (Middle Cambrian to Ordovician, "Arenig") * '' Siphonobolus'' Havlíček, 1982 (Ordovician, "Tremadoc" to "Arenig") * '' Siphonotreta'' de Verneuil, 1845 (Ordovician, "Arenig" to "Caradoc") * '' Siphonotretella'' Popov & Holmer, 1994 (Lower Ordovician, "Tremadoc" to "Arenig")

References

Lingulata {{Paleo-protostome-stub