Phosphatocopina (alternatively Phosphatocopida) is an extinct group of bivalved arthropods known from 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 Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...

period. They are generally sub-milimetric to a few millimetres in size. They are typically only known from isolated carapaces, but some found in

Orsten The Orsten fauna are fossilized organisms preserved in the Orsten lagerstätte of Cambrian (Late Miaolingian to Furongian) rocks, notably at Kinnekulle and on the island of Öland, all in Sweden. The initial site, discovered in 1975 by Klaus M� ...

-type phosphatized preservation have their bodies preserved in high fidelity in three dimensions.

Description

The phosphatized bivalved carapace covered the entire body. Members typically grew to a maximum of in length, though ''

Cyclotron A cyclotron is a type of particle accelerator invented by Ernest Lawrence in 1929–1930 at the University of California, Berkeley, and patented in 1932. Lawrence, Ernest O. ''Method and apparatus for the acceleration of ions'', filed: Januar ...

'' grew up to . In some species, spines were present on the carapace. The head either bore a pair of stalked eyes or a pair of dome-shaped medial eyes. The first appendage pair, dubbed the " antennulae", were

uniramous The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments (called podomeres) are of Latin origin, and may be confused with terms for bones: ''coxa'' (meaning hip, : ...

, with the remaining appendage pairs being

biramous The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments (called podomeres) are of Latin origin, and may be confused with terms for bones: ''coxa'' (meaning hip, ...

. The basipods and

endopod The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments (called podomeres) are of Latin origin, and may be confused with terms for bones: ''coxa'' (meaning hip, : ...

s of the biramous limbs had prominently developed

endite The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments (called podomeres) are of Latin origin, and may be confused with terms for bones: ''coxa'' (meaning hip, : ...

s, while the

exopod The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments (called podomeres) are of Latin origin, and may be confused with terms for bones: ''coxa'' (meaning hip (a ...

s were typically annulated, and bore

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. The earliest larval stages of phosphatocopines are known as "head larva", due to them only having the four pairs of

cephalic A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple animals may no ...

appendages, a feature that is a shared groundplan with most other arthropod groups. Fossilised eggs likely to belong to phosphatocopids have been found in

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 ...

deposits in

Poland Poland, officially the Republic of Poland, is a country in Central Europe. It extends from the Baltic Sea in the north to the Sudetes and Carpathian Mountains in the south, bordered by Lithuania and Russia to the northeast, Belarus and Ukrai ...

Ecology

Phosphatocopines are generally thought to have been nektobenthic (swimming close to the sediment), and have been suggested to have fed on small

particulate organic matter Particulate organic matter (POM) is a fraction of total organic matter operationally defined as that which does not pass through a filter pore size that typically ranges in size from 0.053 millimeters (53 μm) to 2 millimeters. Particulate org ...

, using the endites and spines on their limbs to trap particles. They are thought to have been tolerant of

hypoxic Hypoxia means a lower than normal level of oxygen, and may refer to: Reduced or insufficient oxygen * Hypoxia (environmental), abnormally low oxygen content of a specific environment ** Hypoxia in fish, responses of fish to hypoxia * Hypoxia (medi ...

environments, which was probably their preferred habitat.

Taxonomy

When phosphatocopines were first described, they were suggested to be

ostracods Ostracods, or ostracodes, are a class of the Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 33,000 species (only 13,000 of which are extant) have been identified,Brandão, S.N.; Antonietto, L.S; Nery, D.G.; Santos, S.G.; Karano ...

, but this was rejected after their soft tissue was described. They have often been suggested to be close relatives of

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

s, with the proposed clade containing the two groups dubbed Labrophora. However, their

mandibles In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...

and

maxillae In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxillar ...

are not strongly morphologically differentiated from the other trunk limbs, with differentiated mandibles and maxillae characterising most

crown-group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. ...

mandibulates, including crustaceans, and as such have been alternatively suggested to be stem-group mandibulates. The fact that specimens with preserved soft tissue all appear to be larval

instars An instar (, from the Latin ''wikt:instar#Latin, īnstar'' 'form, likeness') is a developmental stage of arthropods, such as insects, which occurs between each ecdysis, moult (''ecdysis'') until sexual maturity is reached. Arthropods must shed the ...

makes their exact placement uncertain. Several subgroups have been proposed, such as Hesslandonidae and Vestrogothiidae.

Genera

* '' Hesslandona''

, Sweden, China Upper Cambrian (

) * '' Trapezilites'' Orsten, Sweden, Upper Cambrian (Furongian) * ''

'' England, Poland, Upper Cambrian (Furongian) * '' Waldoria'' Orsten, Sweden, Upper Cambrian (Furongian) * '' Veldotron'' Orsten, Sweden, Upper Cambrian (Furongian) * ''

Klausmuelleria ''Klausmuelleria'' is an extinct genus of Cambrian phosphatocopines from the Comley Limestone of the United Kingdom. The genus contains a single species, ''Klausmuelleria salopensis''. Description ''Klausmuelleria'' is roughly 340 micromet ...

Comley Limestone The Comley Limestone is an Early Cambrian Lagerstätte exposed in Comley, Shropshire, England. It is known for its phosphatic microfossils, which can be extracted by acid maceration and are preserved in three dimensions in a similar fashion to ...

, England,

Cambrian Series 2 Cambrian Series 2 is the unnamed 2nd series of the Cambrian. It lies above the Terreneuvian series and below the Miaolingian. Series 2 has not been formally defined by the International Commission on Stratigraphy, lacking a precise lower boundary ...

* '' Vestrogothia'' Orsten, Sweden, China Upper Cambrian (Furongian) * '' Falites'' Orsten, Sweden, Upper Cambrian (Furongian) * '' Dabashanella'' China,

Cambrian Stage 3 Cambrian Stage 3 is the still unnamed third stage of the Cambrian. It succeeds Cambrian Stage 2 and precedes Cambrian Stage 4, although neither its base nor top have been formally defined. The plan is for its lower boundary to correspond approxima ...

* '' Comleyopsis'' Comley limestone, England, Cambrian Series 2 * '' Bidimorpha'' Sweden, Denmark, Middle Cambrian

References

{{Taxonbar, from=Q16888348 Cambrian arthropods Taxa described in 1964