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.
Portunidae is a family of crabs which contains the swimming crabs. Its members include many well-known shoreline crabs, such as the blue crab and velvet crab. Two genera in the family are contrastingly named Scylla and Charybdis; the former contains the economically important species black crab and Scylla paramamosain.
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.
Etyiidae is a prehistoric family of dromiacean crabs only known from Cretaceous and a few Paleocene fossils.
Carpilioidea is a superfamily of crabs containing a single extant family, Carpiliidae and three extinct families. The modern range of the family includes the Indo-Pacific, Western Atlantic and Caribbean Sea. The fossil record of the group extends back at least as far as the Paleocene.
The Aethridae are a family of crabs in their own superfamily, Aethroidea. It contains these 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.
Dairoidea is a superfamily of crabs, comprising two families which each contain a single genus: Dairidae and Dacryopilumnidae (Dacryopilumnus) .
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.
Novactaea is a genus of crabs in the family Xanthidae, containing the following species:
Paractaea is a genus of crabs in the family Xanthidae, containing the following species:
Cyclodius is a genus of crabs in the family Xanthidae, containing the following species:
Liomera is a genus of crabs in the family Xanthidae. It contains the following species:
Gaillardiellus is a genus of crabs in the family Xanthidae, containing the following species:
Speocarcinus is a genus of crabs in the family Pseudorhombilidae, containing six extant species, one fossil species from the Late Miocene, one fossil species from the Eocene (Lutetian) and one fossil species from the Early Eocene (Ypresian):
Macromedaeus is a genus of crabs in the family Xanthidae, containing the following species:
Lophozozymus is a genus of crabs in the family Xanthidae, containing the following species:
Euryplacidae is a family of crabs in the superfamily Goneplacoidea which contains the following genera:
Daldorfia is a genus of parthenopid crab, belonging to the subfamily Daldorfiinae.
