Anomura
Encyclopedia
Anomura is a group of decapod
Decapoda
The decapods or Decapoda are an order of crustaceans within the class Malacostraca, including many familiar groups, such as crayfish, crabs, lobsters, prawns and shrimp. Most decapods are scavengers. It is estimated that the order contains nearly 15,000 species in around 2,700 genera, with...

 crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...

s, including hermit crab
Hermit crab
Hermit crabs are decapod crustaceans of the superfamily Paguroidea. Most of the 1100 species possess an asymmetrical abdomen which is concealed in an empty gastropod shell that is carried around by the hermit crab.-Description:...

s and others. Although the names of many anomurans includes the word crab, all true crab
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...

s are in the sister group to the Anomura, the Brachyura
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...

 (the two groups together form the clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

 Meiura).

Description

The name Anomala reflects the unusual variety of forms in this group; whereas all crabs share some obvious similarities, the various groups of anomurans are quite dissimilar. The name Anomura derives from an old classification in which reptant decapods were divided into Macrura (long-tailed), Brachyura (short-tailed) and Anomura (differently-tailed).

As decapods (meaning ten-legged), anomurans have ten pereiopods, but the last pair of these is often hidden inside the gill chamber (under the carapace
Carapace
A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...

) and is used for keeping the gills clean. Since this arrangement is very rare in true crabs
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...

 (only in the small family Hexapodidae
Hexapodidae
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...

), a "crab" with only eight pereiopods is generally an anomuran.

Classification

The Infraorder Anomura is divided into eight superfamilies:
Superfamily Members Families Photo
Aegloidea Aegla Aeglidae
Aeglidae
Aeglidae is a family of freshwater crustaceans currently restricted to South America. They are the only anomurans to be found in fresh water except for a single hermit crab species, Clibanarius fonticola, on Espiritu Santo island, Vanuatu...

 
Eocarcinoidea
Eocarcinoidea
Eocarcinoidea is a family of fossil decapod crustaceans. Formerly thought to be the earliest true crabs, they are now thought to be the oldest members of the Anomura. Two species are included, each in its own family: Eocarcinus praecursor and Platykotta akaina ....

Eocarcinus
Eocarcinus
Eocarcinus praecursor is a Jurassic species of decapod crustacean, sufficiently distinct from its relatives to be placed in its own family...


Platykotta
Platykotta
Platykotta akaina is a species of decapod crustacean from the Triassic of the United Arab Emirates. It is the oldest known fossil from the infraorder Anomura, and is most closely related to Eocarcinus praecursor.-Stratigraphy:The holotype of P...

Eocarcinidae
Eocarcinus
Eocarcinus praecursor is a Jurassic species of decapod crustacean, sufficiently distinct from its relatives to be placed in its own family...


Platykottidae
Platykotta
Platykotta akaina is a species of decapod crustacean from the Triassic of the United Arab Emirates. It is the oldest known fossil from the infraorder Anomura, and is most closely related to Eocarcinus praecursor.-Stratigraphy:The holotype of P...

 
Galatheoidea
Galatheoidea
Galatheoidea is a superfamily of decapod crustaceans comprising some squat lobsters and the porcelain crabs. Two other families of squat lobsters, Chirostylidae and Kiwaidae, are not closely related to the members of Galatheoidea, and are now placed in other superfamilies...

squat lobster
Squat lobster
Squat lobsters are decapod crustaceans of the families Galatheidae, Chirostylidae and Kiwaidae, including the common genera Galathea and Munida. They are not lobsters at all, but are more closely related to porcelain crabs, hermit crabs and then, more distantly, true crabs...

s
porcelain crab
Porcelain crab
Porcelain crabs are decapod crustaceans in the widespread family Porcellanidae, which superficially resemble true crabs. They are typically less than wide, and have flattened bodies as an adaptation for living in rock crevices...

s
Chirostylidae
Galatheidae
Porcellanidae
Porcelain crab
Porcelain crabs are decapod crustaceans in the widespread family Porcellanidae, which superficially resemble true crabs. They are typically less than wide, and have flattened bodies as an adaptation for living in rock crevices...


† Retrorsichelidae 

Munidopsis serricornis
Munidopsis serricornis
Munidopsis serricornis is a species of squat lobster. It is widely distributed in the world's oceans, being found in the eastern Atlantic Ocean , the western Atlantic Ocean , and the Indo-Pacific...


(Galatheidae)
Hippoidea
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...

mole crabs
sand crab
Sand crab
The common term sand crab can refer to various species of crustacean:* Crustacea of the superfamily Hippoidea, often known as mole crabs* Crabs of the genus Ocypode, also commonly known as ghost crabs...

s
Albuneidae
Albuneidae
Albuneidae is a little-known family of specialized burrowing sand crabs. There are 50 extant species as well as nine fossil species that have been described. Fossil specimens have been described from the Cretaceous, Miocene and Oligocene....


Blepharipodidae
Hippidae
Hippidae
Hippidae is a family of decapod crustaceans, commonly known as "mole crabs" or "sand crabs". They are closely related to the family Albuneidae, with which they are usually joined in the superfamily Hippoidea. The family Hippidae comprises the three genera Emerita, Hippa and Mastigochirus...

 

Blepharipoda occidentalis
Blepharipoda occidentalis
Blepharipoda occidentalis, the spiny sand crab or spiny mole crab, is a species of sand crab or mole crab which lives in the eastern Pacific Ocean, from Central California to Baja California. It is oval in shape, growing up to long and wide. It lives on sandy beaches up to under water, and feeds...


(Blepharipodidae)
Kiwaoidea
Kiwa hirsuta
Kiwa hirsuta is a crustacean discovered in 2005 in the South Pacific Ocean. This decapod, which is approximately long, is notable for the quantity of silky blond setae covering its pereiopods . Its discoverers dubbed it the "yeti lobster" or "yeti crab."-Identification:K...

Kiwa hirsuta
Kiwa hirsuta
Kiwa hirsuta is a crustacean discovered in 2005 in the South Pacific Ocean. This decapod, which is approximately long, is notable for the quantity of silky blond setae covering its pereiopods . Its discoverers dubbed it the "yeti lobster" or "yeti crab."-Identification:K...

Kiwaidae
Kiwa hirsuta
Kiwa hirsuta is a crustacean discovered in 2005 in the South Pacific Ocean. This decapod, which is approximately long, is notable for the quantity of silky blond setae covering its pereiopods . Its discoverers dubbed it the "yeti lobster" or "yeti crab."-Identification:K...

 
Lithodoidea king crab
King crab
King crabs, also called stone crabs, are a superfamily of crab-like decapod crustaceans chiefly found in cold seas. Because of their large size and the taste of their meat, many species are widely caught and sold as food, the most common being the red king crab, Paralithodes camtschaticus.King...

s
Hapalogastridae
Hapalogastridae
Hapalogastridae is a family of decapod crustaceans, containing the following species:*Acantholithodes Holmes, 1895**Acantholithodes hispidus *Dermaturus Brandt, 1850**Dermaturus mandtii Brandt, 1850 — wrinkled crab...


Lithodidae 

Lithodes santolla
(Lithodidae
King crab
King crabs, also called stone crabs, are a superfamily of crab-like decapod crustaceans chiefly found in cold seas. Because of their large size and the taste of their meat, many species are widely caught and sold as food, the most common being the red king crab, Paralithodes camtschaticus.King...

)
Lomisoidea hairy stone crab
Hairy stone crab
The hairy stone crab, Lomis hirta, is a crab-like crustacean that lives in the littoral zone of southern Australia from Bunbury, Western Australia to the Bass Strait. It is the only species in its family...

 
Lomisidae
Paguroidea
Hermit crab
Hermit crabs are decapod crustaceans of the superfamily Paguroidea. Most of the 1100 species possess an asymmetrical abdomen which is concealed in an empty gastropod shell that is carried around by the hermit crab.-Description:...

hermit crab
Hermit crab
Hermit crabs are decapod crustaceans of the superfamily Paguroidea. Most of the 1100 species possess an asymmetrical abdomen which is concealed in an empty gastropod shell that is carried around by the hermit crab.-Description:...

s
coconut crab
Coconut crab
The coconut crab, Birgus latro, is a species of terrestrial hermit crab, also known as the robber crab or palm thief. It is the largest land-living arthropod in the world, and is probably at the upper size limit of terrestrial animals with exoskeletons in today's atmosphere at a weight of up to...

 
Coenobitidae
Coenobitidae
Coenobitidae are a family of hermit crabs, widely known for their terrestrial habits. There are 17 species in two genera:*Coenobita Latreille, 1829*Coenobita brevimanus Dana, 1852*Coenobita carnescens Dana, 1851...


Diogenidae
Paguridae
Paguridae
Paguridae is a family of hermit crabs of the order Decapoda. It contains 542 species in over 70 genera:*Acanthopagurus de Saint Laurent, 1968*Agaricochirus McLaughlin, 1981*Alainopaguroides McLaughlin, 1997...


Parapaguridae
Parapaguridae
Parapaguridae is a family of terrestrial hermit crabs. They have gill chambers that function as lungs. Some genera, such as Bivalvopagurus and Tylaspis, do not inhabit shells...


Pylochelidae
Pylochelidae
Pylochelidae is a family of hermit crabs. Its members are commonly called the symmetrical hermit crabs. They live in all the world's oceans, except the Arctic and the Antarctic, at depths of up to...


Pylojacquesidae
Pylojacquesidae
Pylojacquesidae is a small family of hermit crabs, comprising only two species in two genera. The family was erected in 2001, after two specimens at at the were recognised as being quite distinct from other described hermit crabs...

 

Coenobita clypeatus
(Coenobitidae
Coenobitidae
Coenobitidae are a family of hermit crabs, widely known for their terrestrial habits. There are 17 species in two genera:*Coenobita Latreille, 1829*Coenobita brevimanus Dana, 1852*Coenobita carnescens Dana, 1851...

)


The oldest fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

 attributed to Anomura is Platykotta
Platykotta
Platykotta akaina is a species of decapod crustacean from the Triassic of the United Arab Emirates. It is the oldest known fossil from the infraorder Anomura, and is most closely related to Eocarcinus praecursor.-Stratigraphy:The holotype of P...

, from the Norian
Norian
The Norian is a division of the Triassic geological period. It has the rank of an age or stage . The Norian lasted from 216.5 ± 2.0 to 203.6 ± 1.5 million years ago. It was preceded by the Carnian and succeeded by the Rhaetian.-Stratigraphic definitions:The Norian was named after the Noric Alps in...

Rhaetian
Rhaetian
The Rhaetian is in geochronology the latest age of the Triassic period or in chronostratigraphy the uppermost stage of the Triassic system. It lasted from 203.6 ± 1.5 to 199.6 ± 0.6 million years ago...

 of the United Arab Emirates
United Arab Emirates
The United Arab Emirates, abbreviated as the UAE, or shortened to "the Emirates", is a state situated in the southeast of the Arabian Peninsula in Western Asia on the Persian Gulf, bordering Oman, and Saudi Arabia, and sharing sea borders with Iraq, Kuwait, Bahrain, Qatar, and Iran.The UAE is a...

.

Kiwa hirsuta
Kiwa hirsuta
Kiwa hirsuta is a crustacean discovered in 2005 in the South Pacific Ocean. This decapod, which is approximately long, is notable for the quantity of silky blond setae covering its pereiopods . Its discoverers dubbed it the "yeti lobster" or "yeti crab."-Identification:K...

was discovered in 2005 on a deep sea hydrothermal vent
Hydrothermal vent
A hydrothermal vent is a fissure in a planet's surface from which geothermally heated water issues. Hydrothermal vents are commonly found near volcanically active places, areas where tectonic plates are moving apart, ocean basins, and hotspots. Hydrothermal vents exist because the earth is both...

, and placed in a new family.
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