Portunus is a genus of crabs which includes several important species for fisheries, such as the blue swimming crab and the Gazami crab. Other species, such as the three-spotted crab are caught as bycatch.
Xanthidae is a family of crabs known as gorilla crabs, mud crabs, pebble crabs or rubble crabs. Xanthid crabs are often brightly coloured and are highly poisonous, containing toxins which are not destroyed by cooking and for which no antidote is known. The toxins are similar to the tetrodotoxin and saxitoxin produced by puffer fish, and may be produced by bacteria in the genus Vibrio living in symbiosis with the crabs, mostly V. alginolyticus and V. parahaemolyticus.
Majidae is a family of crabs, comprising around 200 marine species inside 52 genera, with a carapace that is longer than it is broad, and which forms a point at the front. The legs can be very long in some species, leading to the name "spider crab". The exoskeleton is covered with bristles to which the crab attaches algae and other items to act as camouflage.
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 :
Charybdis is a genus of swimming crabs in the family Portunidae. It is named after the monster Charybdis of Greek mythology.
Pagurus is a genus of hermit crabs in the family Paguridae. Like other hermit crabs, their abdomen is not calcified and they use snail shells as protection. These marine decapod crustaceans are omnivorous, but mostly prey on small animals and scavenge carrion. Trigonocheirus and Pagurixus used to be considered subgenera of Pagurus, but the former is nowadays included in Orthopagurus, while the latter has been separated as a distinct genus.
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.
Paguristes is a genus of hermit crab in the family Diogenidae. It includes the following species :
Goneplacidae is a family of crabs of the order Decapoda and the superfamily Goneplacoidea. It includes the following genera:
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.
Carcinidae is a family of crabs belonging to the order Decapoda. It has four subfamilies, including Pirimelinae which was previously treated as a family.
Epialtinae is a subfamily of crabs, containing the following genera:
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:
Actaea is a genus of crabs in the family Xanthidae, containing the following species:
Euryplacidae is a family of crabs in the superfamily Goneplacoidea which consists of 14 existing genera and 31 existing species and 8 fossil genera and 15 fossil species.
