| Hexapus Temporal range: | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Subphylum: | Crustacea |
| Class: | Malacostraca |
| Order: | Decapoda |
| Infraorder: | Brachyura |
| Family: | Hexapodidae |
| Genus: | Hexapus De Haan, 1833 |
| Type species | |
| Cancer sexpes Fabricius, 1798 | |
| Species | |
Hexapus is a genus of crabs in the family Hexapodidae. It contains only three extant species found in the Indo-West Pacific. They inhabit the intertidal and subtidal areas of shorelines.
Like other members of the family, these crabs are easily recognizable due to the complete absence of the last pair of walking legs (pereiopods). They thus only have six walking legs (excluding the claws), unlike the usual eight. Their carapace is subquadrate, wider than it is long, with a rounded anterior. [1]
The following are the species classified under Hexapus. [1]
Hexapus estuarinus is now regarded as a junior synonym of Hexapus sexpes. In addition, the following the species has been transferred to other genera: [1] [7] [8]
Anomura is a group of decapod crustaceans, including hermit crabs and others. Although the names of many anomurans include the word crab, all true crabs are in the sister group to the Anomura, the Brachyura.
Portunidae is a family of crabs which contains the swimming crabs.
The Ocypodidae are a family of semiterrestrial crabs that includes the ghost crabs and fiddler crabs. They are found on tropical and temperate shorelines around the world.
Tuerkayana hirtipes is a species of terrestrial crab.
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.
Discoplax is a genus of terrestrial crabs. It is very closely related to the genus Cardisoma.
Perisesarma is a genus of mangrove crabs in the family Sesarmidae predominantly found in the Indo-Pacific. Some 23 species are described as of late 2006, with two from West Africa: P. kammermani(De Man, 1883) and P. albertiRathbun, 1921. They are typically small, semiterrestrial crabs found on the forest floor at low tide. They eat nearly anything they can, and try to eat anything that does not threaten them — including pencils and other objects dropped on the forest floor. The last species of the genus described is P. samawatiGillikin and Schubart (2004). It can be found in East Africa along with P. guttatum, but its sister species is P. eumolpe from Malaysian mangroves
Potamonautidae is a family of freshwater crabs endemic to Africa, including the islands of Madagascar, the Seychelles, Zanzibar, Mafia, Pemba, Bioko, São Tomé, Príncipe and Sherbro Island. It comprises 18 extant genera and 138 extant species. Fossil remains dating from the Late Miocene period have been attributed to the family Potamonautidae.
The Sesarmidae are a family of crabs, previously included in the Grapsidae by many authors. Several species, namely in Geosesarma, Metopaulias, and Sesarma, are true terrestrial crabs. They do not need to return to the sea even for breeding.
Dromiacea is a group of crabs, ranked as a section. It contains 240 extant and nearly 300 extinct species. Dromiacea is the most basal grouping of Brachyura crabs, diverging the earliest in the evolutionary history, around the Late Triassic or Early Jurassic. Below is a cladogram showing Dromiacea's placement within Brachyura:
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 extends back at least as far as the Paleocene.
Goneplacidae is a family of crabs of the order Decapoda and the superfamily Goneplacoidea. It includes the following genera:
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 distinguished from all other true crabs by the reduction of the thorax, such that only seven sternites are exposed, and only four pairs of pereiopods are present. Not counting the enlarged pair of claws, this leaves only six walking legs, from which the type genus Hexapus, and therefore the whole family, takes its name. Some anomuran "crabs", such as porcelain crabs and king crabs also have only four visible pairs of legs. With the exception of Stevea williamsi, from Mexico, all the extant members are found either in the Indo-Pacific oceans, or around the coast of Africa.
Tanaocheles is a genus of crabs, the only genus in the family Tanaocheleidae. It contains two species, T. bidentata and T. stenochilus. The two species were formerly placed in different families, and they were only shown to be related, and placed in a new subfamily, in 2000.
Matutidae is a family of crabs, sometimes called moon crabs, adapted for swimming or digging. They differ from the swimming crabs of the family Portunidae in that all five pairs of legs are flattened, rather than just the last pair, as in Portunidae. Crabs in the Matutidae are aggressive predators.
Dardanus pedunculatus, the anemone hermit crab, is a species of hermit crab from the Indo-Pacific region. It lives at depths of up to 27 m and collects sea anemones to place on its shell for defence.
Ashtoret is a genus of crabs in the family Matutidae, containing the following species:
Leucosiidae is a family of crabs containing three subfamilies and a number of genera incertae sedis:
Goniodromites is an extinct genus of crabs. A new species, G. kubai, which existed during the Oxfordian stage of what is now Poland, was described by Natalia Starzyk, Ewa Krzemiska and Wiesław Krzemiski in 2012.