Grapsoidea is a superfamily

Taxonomic rank

In biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...

 of crab

Crab

True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...

s. These crabs are well known and contain many taxa which are terrestrial (land-living), semi-terrestrial (taking to the sea only for reproduction) or limnic (living in fresh water

Fresh Water

Fresh Water is the debut album by Australian rock and blues singer Alison McCallum, released in 1972. Rare for an Australian artist at the time, it came in a gatefold sleeve...

). Another well-known member with a more conventional lifestyle is the Chinese mitten crab

Chinese mitten crab

The Chinese mitten crab, Eriocheir sinensis is a medium-sized burrowing crab, named for its furry claws that look like mittens, that is native in the coastal estuaries of eastern Asia from Korea in the north to the Fujian province of China in the south...

, Eriocheir sinensis.

The delimitation of the Grapsidae

Grapsidae

Grapsidae is a family of crabs known variously as marsh crabs, shore crabs or talon crabs. It is not confirmed that the family forms a monophyletic group and some taxa may belong in other families...

 and Plagusiidae

Plagusiidae

Plagusiidae is a family of crabs. It was formerly treated as a subfamily of the family Grapsidae, but has since been considered sufficiently distinct to be a family in its own right.Five genera are included in the family:*Davusia Guinot, 2007...

 is in need of revision; the last at least is not monophyletic. The same apparently holds true for several genera

Genera

Genera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...

 in the Sesarmidae

Sesarmidae

Sesarmidae is a family of crabs, previously included in the Grapsidae by many authors. Several species, namely in Geosesarma, Metopaulias and Sesarma, are true terrestrial crabs. They do not need to return to the sea even for breeding.-Genera:...

.

The closest living relatives of the Grapsoidea are the Ocypodoidea

Ocypodoidea

Ocypodoidea is a superfamily of crabs, named after the genus Ocypode. It contains over 300 extant species in the following eight families:* Camptandriidae Stimpson, 1858* Dotillidae Stimpson, 1858* Heloeciidae H. Milne-Edwards, 1852...

. In fact, they seem to be paraphyletic with respect to each other and it seems warranted to merge the Ocypodoidea into the Grapsoidea.