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 ...
of
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 ...
s,
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 ...
s,
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
Mouthparts may refer to:
* The parts of a mouth
** Arthropod mouthparts
*** Insect mouthparts
{{disambig ...
, 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.

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
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 ...
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: 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 ...
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.''
Order Decapoda Latreille, 1802
*Suborder 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 ...
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
See also
* List of Atlantic decapod species
* Phylogeny of Malacostraca
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