Portunus is a genus of crab which includes several important species for fisheries, such as the blue swimming crab, Portunus pelagicus and the Gazami crab, P. trituberculatus. Other species, such as the three-spotted crab (P. sanguinolentus) are caught as bycatch.
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.
Cancridae is a family of crabs. It comprises six extant genera, and ten exclusively fossil genera, in two subfamilies:
Leucosioidea is a superfamily of crabs containing the two families Leucosiidae and Iphiculidae.
Retroplumidae is a family of heterotrematan crabs, placed in their own (monotypic) superfamily, Retroplumoidea.
The thumbnail crab, Thia scutellata, is a species of crab whose carapace resembles a human thumbnail. It is found in the North Sea, north-east Atlantic and Mediterranean Sea. It is the only extant species in the genus Thia, although two fossil species are known.
Calappidae is a family of crabs containing 16 genera, of which 7 are only known as fossils:
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.
Cheiragonidae is a small family of crabs, sometimes called helmet crabs, placed in its own superfamily, Cheriagonoidea. It comprises three extant species, Erimacrus isenbeckii, Telmessus acutidens and Telmessus cheiragonus, there are no yet evidences of Cheiragonidae in the fossil record. Many of these crabs were formerly treated as members of the Atelecyclidae.
Goneplacoidea is a superfamily of crabs containing 11 extant families, and two families known only from fossils.
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.
Glaessneropsoidea is a superfamily of fossil crabs. They are found in rocks from Late Jurassic age to Late Cretaceous. The 45 species in the superfamily are divided among 11 genera in four families:
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 recognised in three families:
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 subfamilies in a Palicidae of wider circumscription.
Dromia is a genus of crabs in the family Dromiidae. It contains 6 extant species:
Metopograpsus is a genus of crabs, containing the following extant species:
Goneplax is a genus of crabs, containing the following extant species:
Mathildellidae is family of crabs belonging to the superfamily Goneplacoidea, containing the following genera:
Ethusidae is one of two extant families of crabs in the superfamily Dorippoidea. It contains four genera. Members of this family are found in marine environments at depths from 16m to 4,192m.
