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:
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.
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.
Trapezia is a genus of guard crabs in the family Trapeziidae. Like other members of this family, they live in association with corals, feeding on coral tissue and mucus, and defending the corals from predators, like starfish. It contains the following species:
Calappidae is a family of crabs containing 16 genera, of which 7 are only known as fossils:
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.
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.
Etisus is a genus of crabs, containing the following extant species:
Pugettia is a genus of kelp crabs in the family Epialtidae. It comprises the following species:
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:
Chlorodiella is a genus of crabs in the family Xanthidae, containing the following species:
Medaeus is a genus of crabs in the family Xanthidae, containing the following species:
Leptodius is a genus of crabs in the family Xanthidae, containing the following species:
Microcassiope 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:
Pisinae is a subfamily of crabs in the family Epialtidae, comprising the following genera:
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.
