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.
Eriocheir is a genus of crabs, including the Chinese mitten crab, E. sinensis. Formerly in the family Grapsidae, it is now placed in the Varunidae.
Cronius is a genus of crabs containing the two species Cronius ruber and Cronius tumidulus.
Hymenosomatidae is a family of crabs with some 110 described species in nearly 20 genera. The following genera are placed in the Hymenosomatidae:
Maja is a genus of majid crabs erected by Jean-Baptiste Lamarck in 1801. It includes the following extant species:
Cancridae is a family of crabs. It comprises six extant genera, and ten exclusively fossil genera, in two subfamilies:
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.
Discoplax is a genus of terrestrial crabs. It is very closely related to the genus Cardisoma.
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.
Goneplacoidea is a superfamily of crabs containing 11 extant families, and two families known only from fossils.
Dairoidea is a superfamily of crabs, comprising two families which each contain a single genus: Dairidae and Dacryopilumnidae (Dacryopilumnus) .
Dakoticancroidea is a superfamily of fossil crabs, containing six species in five genera, divided into two families. The family Dakoticancridae is only known from North American rocks of Late Cretaceous age, while the single species in the Ibericancridae was found in Spain.
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.
Macropodia is a genus of crabs, belonging to the family Inachidae. It contains the following species:
Cyrtocarcinus truncatus is a species of crab in the family Xanthidae that lives in the waters around Hawaii. It was described in 1906 by Mary J. Rathbun as Harrovia truncata, based on a single immature male specimen caught near Kauai. Masatsune Takeda transferred the species to his new genus Glyptocarcinus in 1979, and Peter Ng and Diana Chia erected a new genus, Cyrtocarcinus, for this species alone, in 1994.
Demania is a genus of crabs in the family Xanthidae, containing the following species:
Dynomenidae is a family of crabs in the superfamily Dromioidea mostly found in Madagascar. There are nineteen genera in this family: five extant and fourteen known from fossils:
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.
