A fiddler crab, sometimes known as a calling crab, may be any of more than one hundred species of semiterrestrial marine crabs in the family Ocypodidae. A smaller number of ghost crab and mangrove crab species are also found in the family Ocypodidae. This entire group is composed of small crabs, the largest being slightly over two inches (5 cm) across. Fiddler crabs are found along sea beaches and brackish intertidal mud flats, lagoons and swamps. Fiddler crabs are most well known for their sexually dimorphic claws; the males' major claw is much larger than the minor claw, while the females' claws are both the same size.
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.
Pinnotheres is a genus of crabs, including the pea crab. Many species formerly in Pinnotheres have been placed in new genera, such as Zaops ostreus, the oyster crab and Nepinnotheres novaezelandiae, the New Zealand pea crab. The species currently recognised in the genus Pinnotheres are:
Macrophthalmus is a genus of crabs which are widespread across the Indo-Pacific. It contains the following species :
Ozius is a genus of crabs in the family Menippidae, containing the following 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.
Dairoidea is a superfamily of crabs, comprising two families which each contain a single genus: Dairidae and Dacryopilumnidae (Dacryopilumnus) .
Actaea is a genus of crabs in the family Xanthidae, containing the following species:
Chlorodiella is a genus of crabs in the family Xanthidae, containing the following species:
Liomera is a genus of crabs in the family Xanthidae, containing the following species:
Paraxanthias is a genus of crabs in the family Xanthidae, containing one exclusively fossil species and the following extant species:
Atergatis is a genus of crabs in the family Xanthidae, containing the following species:
Atergatopsis is a genus of crabs in the family Xanthidae, containing the following species:
Platypodia is a genus of crabs in the family Xanthidae, containing the following species:
Hippa is a genus of decapod crustaceans in the family Hippidae, containing the following species:
Pilumnus is a genus of crabs, containing the following species:
Ebalia is a genus of crab in the family Leucosiidae.
Elamena is a genus of crab, 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.
