The Decapoda or decapods (literally "ten-footed") are an

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

s within the class

Malacostraca Malacostraca (from New Latin; ) is the largest of the six classes of crustaceans, containing about 40,000 living species, divided among 16 orders. Its members, the malacostracans, display a great diversity of body forms and include crabs, lobst ...

, including many familiar groups, such as

crab Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the thorax. They live in all the ...

lobster Lobsters are a family (biology), family (Nephropidae, Synonym (taxonomy), synonym Homaridae) of marine crustaceans. They have long bodies with muscular tails and live in crevices or burrows on the sea floor. Three of their five pairs of legs ...

crayfish Crayfish are freshwater crustaceans belonging to the clade Astacidea, which also contains lobsters. In some locations, they are also known as crawfish, craydids, crawdaddies, crawdads, freshwater lobsters, mountain lobsters, rock lobsters, mu ...

shrimp Shrimp are crustaceans (a form of shellfish) with elongated bodies and a primarily swimming mode of locomotion – most commonly Caridea and Dendrobranchiata of the decapod order, although some crustaceans outside of this order are refer ...

and

prawns Prawn is a common name for small aquatic crustaceans with an exoskeleton and ten legs (which is a member of the order decapoda), some of which can be eaten. The term "prawn"Mortenson, Philip B (2010''This is not a weasel: a close look at nature ...

. Most decapods are

scavenger Scavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a herbivorous feeding b ...

s. The order is estimated to contain nearly 15,000 species in around 2,700 genera, with around 3,300 fossil species. Nearly half of these species are crabs, with the shrimp (about 3,000 species) and Anomura including hermit crabs, porcelain crabs, squat lobsters (about 2500 species) making up the bulk of the remainder. The earliest

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

decapod is the

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 ...

'' Palaeopalaemon''.

Anatomy

Decapods can have as many as 38 appendages, arranged in one pair per body segment. As the name Decapoda (from the Greek , ', "ten", and , '' -pod'', "foot") implies, ten of these appendages are considered legs. They are the

pereiopod The decapod (crustaceans such as a crab, lobster, shrimp or prawn) is made up of 20 body segments grouped into two main body parts: the cephalothorax and the pleon (abdomen). Each segment may possess one pair of appendages, although in various g ...

s, found on the last five thoracic segments. In many decapods, one pair of these "legs" has enlarged pincers, called

chelae A chela ()also called a claw, nipper, or pinceris a pincer (biology), pincer-like organ at the end of certain limbs of some arthropods. The name comes from Ancient Greek , through New Latin '. The plural form is chelae. Legs bearing a chela are ...

, with the legs being called chelipeds. In front of the pereiopods are three pairs of

maxilliped An appendage (or outgrowth) is an external body part, or natural prolongation, that protrudes from an organism's body. In arthropods, an appendage refers to any of the homologous body parts that may extend from a body segment, including anten ...

s that function as feeding appendages. The head has five pairs of appendages, including mouthparts, antennae, and antennules. There are five more pairs of appendages on the abdomen. They are called

pleopod The decapod ( crustaceans such as a crab, lobster, shrimp or prawn) is made up of 20 body segments grouped into two main body parts: the cephalothorax and the pleon (abdomen). Each segment may possess one pair of appendages, although in various ...

s. There is one final pair called

uropod Uropods are posterior appendages found on a wide variety of crustaceans. They typically have functions in locomotion. Definition Uropods are often defined as the appendages of the last body segment of a crustacean. An alternative definition sugge ...

s, which, with the

telson The telson () is the posterior-most division of the body of an arthropod. Depending on the definition, the telson is either considered to be the final segment of the arthropod body, or an additional division that is not a true segment on accou ...

, form the tail fan. Haeckel Decapoda

Evolution

Decapods originated in the

Late 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. The ...

around 455 million years ago, with the

Dendrobranchiata Dendrobranchiata is a suborder of Decapoda, decapods, commonly known as prawns. There are 540 extant species in seven families, and a fossil record extending back to the Devonian. They differ from related animals, such as Caridea and Stenopodidea ...

(prawns) being the first group to diverge. The remaining group, called Pleocyemata, then diverged between the swimming

groupings and the crawling/walking group called Reptantia, consisting of

lobsters Lobsters are a family (Nephropidae, synonym Homaridae) of marine crustaceans. They have long bodies with muscular tails and live in crevices or burrows on the sea floor. Three of their five pairs of legs have claws, including the first pair, ...

and crabs. High species diversification can be traced to the

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...

and

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

periods, which coincides with the rise and spread of modern

coral reefs A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of Colony (biology), colonies of coral polyp (zoology), polyps held together by calcium carbonate. Most coral reefs are built from stony corals, wh ...

, a key habitat for the decapods. The cladogram below results from analysis by Wolfe ''et al.'' (2019).

Classification

Classification within the order Decapoda depends on the structure of the

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

s and legs, and the way in which the

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

e develop, giving rise to two suborders:

and Pleocyemata. The Dendrobranchiata consist of prawns, including many species colloquially referred to as "shrimp", such as the "white shrimp", ''

Litopenaeus setiferus ''Litopenaeus setiferus'' (also accepted: ''Penaeus setiferus'', and known by various common names including Atlantic white shrimp, '' white shrimp'', ''gray shrimp'', ''lake shrimp'', ''green shrimp'', ''green-tailed shrimp'', ''blue-tailed s ...

''. The Pleocyemata include the remaining groups, including "true shrimp". Those groups that usually walk rather than swim (Pleocyemata, excluding Stenopodidea and Caridea) form a clade called Reptantia. This classification to the level of superfamilies follows De Grave ''et al.'' Penaeus vannamei 01

Blue crab on market in Piraeus - Callinectes sapidus Rathbun 20020819-317

Order Decapoda Latreille, 1802 *Suborder

Bate, 1888 **

Penaeoidea Penaeoidea is the larger of the two superfamilies of prawns. It comprises eight families, three of which are known only from fossils. The fossil record of the group stretches back to ''Aciculopoda'', discovered in Famennian sediments in Oklahoma ...

Rafinesque, 1815 **

Sergestoidea Sergestoidea is a superfamily of prawns, divided into two families – the Luciferidae and the Sergestidae Sergestidae is a family of prawns which have lived since at least the Middle Jurassic (Bajocian/Bathonian). It contains the following g ...

Dana, 1852 *Suborder Pleocyemata Burkenroad, 1963 **Infraorder Stenopodidea Bate, 1888 **Infraorder Caridea Dana, 1852 *** Procaridoidea Chace & Manning, 1972 *** Galatheacaridoidea Vereshchaka, 1997 *** Pasiphaeoidea Dana, 1852 *** Oplophoroidea Dana, 1852 *** Atyoidea De Haan, 1849 *** Bresilioidea Calman, 1896 *** Nematocarcinoidea Smith, 1884 *** Psalidopodoidea Wood-....., 1874 *** Stylodactyloidea Bate, 1888 *** Campylonotoidea Sollaud, 1913 *** Palaemonoidea Rafinesque, 1815 *** Alpheoidea Rafinesque, 1815 ***

Processoidea The Processidae are a family of shrimp, comprising 65 species in five genera, and the only family in the superfamily Processoidea. They are small, nocturnal animals, mostly living in shallow seas, particularly on grass flats. The first pereiopods ...

Ortmann, 1896 *** Pandaloidea Haworth, 1825 *** Physetocaridoidea Chace, 1940 ***

Crangonoidea Crangonoidea is a superfamily of shrimp containing the two families Crangonidae and Glyphocrangonidae Glyphocrangonidae is a family of crustaceans belonging to the order Decapoda The Decapoda or decapods (literally "ten-footed") are an o ...

Haworth, 1825 **Infraorder Astacidea Latreille, 1802 *** Enoplometopoidea de Saint Laurent, 1988 *** Nephropoidea Dana, 1852 *** Astacoidea Latreille, 1802 *** Parastacoidea Huxley, 1879 **Infraorder Glypheidea Winckler, 1882 *** Glypheoidea Winckler, 1882 **Infraorder Axiidea de Saint Laurent, 1979b **Infraorder

Gebiidea Gebiidea is an infraorder of Decapoda, decapod crustaceans. Gebiidea and Axiidea are divergent infraoders of the former infraorder Thalassinidea. These infraorders have converged Ecology, ecologically and Morphology (biology), morphologically as ...

de Saint Laurent, 1979 **Infraorder Achelata Scholtz & Richter, 1995 **Infraorder Polychelida Scholtz & Richter, 1995 **Infraorder Anomura MacLeay, 1838 *** Aegloidea Dana, 1852 *** Galatheoidea Samouelle, 1819 ***

Hippoidea Hippoidea is a superfamily of decapod crustaceans known as sand crabs or mole crabs. Ecology Hippoids are adapted to burrowing into sandy beaches, a habit they share with raninid crabs, and the parallel evolution of the two groups is striking. ...

Latreille, 1825a *** Chirostyloidea Ortmann, 1892 *** Lithodoidea Samouelle, 1819 *** Lomisoidea Bouvier, 1895 *** Paguroidea Latreille, 1802 **Infraorder Brachyura Linnaeus, 1758 ***Section Dromiacea De Haan, 1833 ****

Dromioidea Dromioidea is a superfamily of crabs mostly found in Madagascar. Dromioidea belongs the group Dromiacea, taxonomically ranked as a section, which is the most basal grouping of Brachyura crabs. Dromiacea likely diverged from the rest of Brach ...

De Haan, 1833 ****

Homolodromioidea Homolodromiidae is a family of crabs, the only family in the superfamily Homolodromioidea. In contrast to other crabs, including the closely related Homolidae, there is no strong ''linea homolica'' along which the exoskeleton breaks open during e ...

Alcock, 1900 ****

Homoloidea Homoloidea is a superfamily of dromiacean crabs. Homoloidea belongs the group Dromiacea, taxonomically ranked as a section, and is the sister group to Dromioidea. Dromiacea is the most basal grouping of Brachyura crabs, and likely diverged fr ...

De Haan, 1839 ***Section

Raninoida Raninoida is a taxonomic section of the crabs, containing a single superfamily, Raninoidea. This group of crabs is unlike most, with the abdomen not being folded under the thorax. It comprises 46 extant species, and nearly 200 species known only ...

De Haan, 1839 ***Section

Cyclodorippoida Cyclodorippoida is a group of crabs, ranked as a section. It contains the single superfamily Cyclodorippoidea, which holds three families, Cyclodorippidae, Cymonomidae and Phyllotymolinidae. Below is a cladogram A cladogram (from Greek ' ...

Ortmann, 1892 ***Section

Eubrachyura Eubrachyura is a group of decapod crustaceans (ranked as a "section") comprising the more derived crabs. It is divided into two subsections, based on the position of the genital openings in the two sexes. In the Heterotremata, the openings are o ...

de Saint Laurent, 1980 ****Subsection

Heterotremata Heterotremata is a clade of crabs, comprising those crabs in which the genital openings are on the sternum in females, but on the legs in males. It comprises 68 families in 28 superfamilies. Evolution Heterotremata is the sister group to Thorac ...

Guinot, 1977 *****

Aethroidea The Aethridae are a family of crabs in their own superfamily, Aethroidea. It contains these genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hie ...

Dana, 1851 *****

Bellioidea Belliidae is a family of crabs of the order Decapoda. They respond to predators by hyper-extending all of its limbs and remain in this position for varied amounts of time (Hazlett). Species Seven species belong to the family Belliidae : *'' ...

Dana, 1852 *****

Bythograeoidea The Bythograeidae are a small family of blind crabs which live around hydrothermal vents. The family contains 16 species in six genera. Their relationships to other crabs are unclear. They are believed to eat bacteria and other vent organisms. ...

Williams, 1980 *****

Calappoidea Calappoidea is a superfamily of crabs comprising the two families Calappidae and Matutidae. The earliest fossils attributable to the Calappoidea date from the Aptian The Aptian is an age in the geologic timescale or a stage in the stratigraph ...

De Haan, 1833 *****

Cancroidea Cancroidea is a superfamily of crabs, comprising the families Atelecyclidae and Cancridae. http://boletinsgm.igeolcu.unam.mx/bsgm/vols/epoca04/6502/%2810%29Osso.pdf Four other families have been separated into new superfamilies: Cheiragonidae ...

Latreille, 1802 *****

Carpilioidea Carpilioidea is a superfamily of crabs containing a single extant family, Carpiliidae and three extinct families. The modern range of the family includes the Indo-Pacific, Western Atlantic and Caribbean Sea. The fossil record of the group ext ...

Ortmann, 1893 *****

Cheiragonoidea Cheiragonidae is a small family (biology), family of crabs, sometimes called ''helmet crabs'', placed in its own Taxonomic rank, superfamily, Cheriagonoidea. It comprises three extant species, ''Horsehair crab, Erimacrus isenbeckii'', ''Telmessus ...

Ortmann, 1893 *****

Corystoidea Corystidae is a family of crabs, in its own superfamily, Corystoidea. It includes what was once thought to be the oldest Eubrachyuran fossil, '' Hebertides jurassica'', thought to be dating from the Bathonian ( Middle Jurassic); the species was ...

Samouelle, 1819 *****

Dairoidea Dairoidea is a superfamily of crabs, comprising two families which each contain a single genus: Dairidae (the living fossil '' Daira'' ) and Dacryopilumnidae ('' Dacryopilumnus'') . Species ; Dairidae *''Daira americana'' Stimpson, 1 ...

Serène, 1965 *****

Dorippoidea Dorippoidea is a superfamily of crabs. The earliest fossils attributable to the Dorippoidea date from the Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the ge ...

MacLeay, 1838 *****

Eriphioidea Eriphioidea is a superfamily of crabs, containing the six families Dairoididae, Eriphiidae, Hypothalassiidae, Menippidae, Oziidae and Platyxanthidae. They are united by a number of characters, including a marked difference in size between t ...

MacLeay, 1838 *****

Gecarcinucoidea Gecarcinucoidea is a superfamily of freshwater crabs. Its members have been grouped into families in various ways, with some authors recognizing families such as "Deckeniidae", "Sundathelphusidae", and "Parathelphusidae", but now only the family ...

Rathbun, 1904 *****

Goneplacoidea Goneplacoidea is a superfamily of crabs containing 11 extant families, and two families known only from fossils (marked "†"). * Acidopsidae * † Carinocarcinoididae * Chasmocarcinidae * Conleyidae * Euryplacidae * Goneplacidae * Litoche ...

MacLeay, 1838 *****

Hexapodoidea Hexapodidae is a family of crabs, the only family in the superfamily Hexapodoidea. It has traditionally been treated as a subfamily of the family Goneplacidae, and was originally described as a subfamily of Pinnotheridae. Its members can be ...

Miers, 1886 *****

Leucosioidea Leucosioidea is a superfamily of crab Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entire ...

Samouelle, 1819 *****

Majoidea The Majoidea are a Superfamily (taxonomy), superfamily of crabs which includes the various spider crabs. Taxonomy In "''A classification of living and fossil genera of decapod crustaceans''" De Grave and colleagues divided Majoidea into six fa ...

Samouelle, 1819 *****

Orithyioidea ''Orithyia sinica'', sometimes called tiger crab or the tiger face crab, is a "singularly unusual" species of crab, whose characteristics warrant its separation into a separate genus, family and even superfamily, having previously been included ...

Dana, 1852c *****

Palicoidea Palicoidea is a superfamily of crabs, comprising the two families Crossotonotidae and Palicidae. Together, they contain 13 genera, including two genera in the Palicidae known only from fossils. The two families were previously treated as two ...

Bouvier, 1898 *****

Parthenopoidea Parthenopidae is a family of crabs, placed in its own Superfamily (taxonomy), superfamily, Parthenopoidea. It comprises nearly 40 genera, divided into two subfamilies, with three genera ''incertae sedis'': ;Daldorfiinae Ng & Rodríguez, 1986 * ...

MacLeay, *****

Pilumnoidea Pilumnoidea is a superfamily of crabs, whose members were previously included in the Xanthoidea. The three families are unified by the free articulation of all the segments of the male crab's abdomen and by the form of the gonopods. The earlies ...

Samouelle, 1819 *****

Portunoidea __NOTOC__ Portunoidea is a superfamily of crabs that includes the family Portunidae, the swimming crabs. Which other crab families are also placed here is a matter of some contention, and may be revised following molecular phylogenetic analyses. ...

Rafinesque, 1815 ***** Potamoidea Ortmann, 1896 *****

Pseudothelphusoidea Pseudothelphusidae is a family of freshwater crabs found chiefly in mountain streams in the Neotropics. They are believed to have originated in the Greater Antilles and then crossed to Central America via a Pliocene land bridge. Parasitology Ps ...

Ortmann, 1893 *****

Pseudozioidea Pseudozioidea is a superfamily of crabs, formerly treated in the Eriphioidea, Carpilioidea, Xanthoidea, Pilumnoidea and Goneplacoidea. A number of fossils from the Eocene onwards are known from the family Pseudoziidae. Eleven genera are rec ...

Alcock, 1898 *****

Retroplumoidea Retroplumidae is a family of heterotrematan crabs, placed in their own (monotypic) superfamily, Retroplumoidea. Classification Eight genera are recognised, of which all but two are only known from fossils: *'' Archaeopus'' † Rathbun, 1908 *'' ...

Gill, 1894 *****

Trapezioidea Trapezioidea is a superfamily (zoology), superfamily of crabs. Its members live symbiosis, symbiotically with corals, and have a fossil record stretching back to the Eocene. Families The World Register of Marine Species lists the following famil ...

Miers, 1886 *****

Trichodactyloidea Trichodactylidae is a family of crabs, in its own superfamily, Trichodactyloidea. They are all freshwater animals from Central and South America, including some offshore islands, such as Ilhabela, São Paulo. Only one of the 50 species is known f ...

H. Milne-Edwards, 1853 ***** Xanthoidea MacLeay, 1838 ****Subsection

Thoracotremata Thoracotremata is a clade of crabs, comprising those crabs in which the genital openings in both sexes are on the sternum, rather than on the legs. It comprises 17 families in four superfamilies . Evolution Thoracotremata is the sister gro ...

Guinot, 1977 *****

Cryptochiroidea Cryptochiridae is a family of crabs known commonly as gall crabs or coral gall crabs. They live inside dwellings in corals and cause the formation of galls in the coral structure.Johnsson, R., et al. (2006)The association of two gall crabs (Bra ...

Paul'son, 1875 *****

Grapsoidea The Grapsoidea are a superfamily of crabs; they are well known and contain many taxa which are terrestrial (land-living), semiterrestrial (taking to the sea only for reproduction), or limnic (living in fresh water). Another well-known member w ...

MacLeay, 1838 *****

Ocypodoidea The Ocypodoidea, or ocypoid crabs, are a superfamily of crabs, named after the genus ''Ocypode''. It contains over 300 extant species in these eight families: * Camptandriidae Stimpson, 1858 * Dotillidae Stimpson, 1858 * Heloeciidae H. Milne-Ed ...

Rafinesque, 1815 ***** Pinnotheroidea De Haan, 1833

References

External links

*
Decapod Crustacea
"Tree of Life" page at the Natural History Museum of Los Angeles County * {{Authority control Crustacean orders Malacostraca Extant Devonian first appearances Taxa named by Pierre André Latreille

Anatomy

Evolution

Classification

See also

References

External links