Porcelain crabs are decapod crustaceans in the widespread family Porcellanidae, which superficially resemble true crabs. They have flattened bodies as an adaptation for living in rock crevices. They are delicate, readily losing limbs when attacked, and use their large claws for maintaining territories. They first appeared in the Tithonian age of the Late Jurassic epoch, 145–152 million years ago.
The Ocypodoidea, or ocypoid crabs, are a superfamily of crabs, named after the genus Ocypode. It contains the following families:
The Diogenidae are a family of hermit crabs, sometimes known as "left-handed hermit crabs" because in contrast to most other hermit crabs, its left chela (claw) is enlarged instead of the right. It comprises 429 extant species, and a further 46 extinct species, making it the second-largest family of marine hermit crabs, after the Paguridae.
The Grapsidae are a family of crabs known variously as marsh crabs, shore crabs, or talon crabs. The family has not been confirmed to form a monophyletic group and some taxa may belong in other families. They are found along the shore among rocks, in estuaries, marshes, and in some cases pelagic among drifting seaweeds and flotsam.
Macrophthalmus is a genus of crabs which are widespread across the Indo-Pacific. It contains the following species : Species in this genus are often referred to as sentinel crabs.
Menippidae is a family of crabs of the order Decapoda.
Ozius is a genus of crabs in the family Menippidae, containing the following species:
Dromiidae is a family of crabs, often referred to as sponge crabs. They are small or medium-sized crabs which get their name from the ability to shape a living sponge into a portable shelter for themselves. A sponge crab cuts out a fragment from a sponge and trims it to its own shape using its claws. The last two pairs of legs are shorter than other legs and bend upward over the crab's carapace, to hold the sponge in place. The sponge grows along with the crab, providing a consistent shelter.
The Varunidae are a family of thoracotrematan crabs. The delimitation of this family, part of the taxonomically confusing Grapsoidea, is undergoing revision. For a long time, they were placed at the rank of subfamily in the Grapsidae, but they appear to be closest to Macropthalmus and the Mictyridae, which are usually placed in the Ocypodoidea. It may thus be better to merge the latter superfamily with the Grapsoidea, retaining the latter name as it is older.
Herbstia is a genus of crabs, containing the following eleven species:
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 earliest fossils assigned to this group are of Eocene age.
Actumnus is a genus of crabs in the family Pilumnidae. Alongside the 28 extant species, it has a fossil record extending back into the Miocene.
The Dotillidae are a family of crabs with 59 species, nearly half of which are in the genus Ilyoplax. The two genera Scopimera and Dotilla are collectively the sand bubbler crabs, which leave conspicuous collections of sand pellets on sandy beaches across the tropical and subtropical Indo-Pacific.
Metopograpsus is a genus of crabs, containing the following extant species:
Pachygrapsus is a genus of small shore crabs. Recent genetic data suggest this genus to be possibly polyphyletic.
The Galatheoidea are a superfamily of decapod crustaceans comprising the porcelain crabs and some squat lobsters. Squat lobsters within the three families of the superfamily Chirostyloidea are not closely related to the squat lobsters within the Galatheoidea. The fossil record of the superfamily extends back to the Middle Jurassic genus Palaeomunidopsis.
Leucosiidae is a family of crabs containing three subfamilies and a number of genera incertae sedis:
Paraxanthias is a genus of crabs in the family Xanthidae, containing one exclusively fossil species and the following extant species:
Inachoididae is a family of crabs originally erected by James Dwight Dana in 1852. It was not recognised as a valid family until the early 1980s. Its members closely resemble those of the family Inachidae, and the Inachoididae could be recognised as a subfamily of that family.
The Camptandriidae are a family of crabs, with 38 species in 21 genera:
