Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting tail-like abdomen, usually hidden entirely under the thorax. They live in all the world's oceans, in freshwater, and on land, are generally covered with a thick exoskeleton, and have a single pair of pincers on each arm. They first appeared during the Jurassic period, around 200 million years ago.
Anomura is a group of decapod crustaceans, including hermit crabs and others. Although the names of many anomurans include the word crab, all true crabs are in the sister group to the Anomura, the Brachyura.
Mictyris is a genus of brightly coloured crabs, placed in its own taxonomical family, the Mictyridae. It inhabits the central Indo-West Pacific region. These crabs congregate on mud flats or beaches in groups of a few thousand, and filter sand or mud for microscopic organisms. They congregate during low tide, and bury themselves in the sand during high tide or whenever they are threatened. This is done in wet sand, and they dig in a corkscrew pattern, leaving many small round pellets of sand behind them.
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.
The Majoidea are a superfamily of crabs which includes the various spider crabs.
Lithodes santolla, also known as the southern king crab, Chilean king crab or centolla, is a species of king crab, found off southern South America including the offshore Falkland Islands. On the Pacific side, it is found in Chile from Talcahuano to Cape Horn. On the Atlantic side, it is found off Argentina and Uruguay. It lives in the benthic zone at depths of 0–700 m (0–2,300 ft), with Uruguayan records being exclusively from great depths. In Chile, it mostly lives at depths to 150 m (490 ft), but south of 40° S it can be found to 600 m (2,000 ft). It is a large crab that can reach up to 19 cm (7.5 in) in carapace length, and it is the target of commercial fishing.
Heterotremata is a clade of crabs, comprising those crabs in which the genital openings are on the sternum in females, but on the legs in males. It comprises 68 families in 28 superfamilies.
Maguimithrax spinosissimus, also known as the Caribbean king crab, West Indian spider crab, channel clinging crab, reef or spiny spider crab, and coral crab, is a species of spider crab that occurs throughout South Florida and across the Caribbean Islands.
Trapezioidea is a superfamily of crabs. Its members live symbiotically with corals, and have a fossil record stretching back to the Eocene.
The Pylojacquesidae are a small family of hermit crabs, comprising only two monotypic genera. The family was erected in 2001, after two specimens at Museum für Naturkunde at the Humboldt University of Berlin were recognised as being quite distinct from other described hermit crabs. The family members differ from other hermit crabs in that their mandibles are chitinous and toothed.
Aethra is a genus of crabs in the family Aethridae, containing the following species:
The Panopeidae are a family containing 26 genera of morphologically similar crabs, often known as "mud crabs". Their centers of diversity are the Atlantic Ocean and eastern Pacific Ocean.
Dyspanopeus sayi is a species of mud crab that is native to the Atlantic coast of North America. It has also become established outside its native range, living in Swansea Docks since 1960, the Mediterranean Sea since the 1970s, the North Sea since 2007 and the Black Sea since 2010. It can reach a carapace width of 20 mm (0.8 in), and has black tips to its unequal claws. It feeds on bivalves and barnacles, and is in turn eaten by predators including the Atlantic blue crab, Callinectes sapidus. Eggs are produced from spring to autumn, the offspring reach sexual maturity the following summer, and individuals can live for up to two years. The closest relative of D. sayi is D. texanus, which lives in the Gulf of Mexico; the two species differ in subtle features of the genitalia and the last pair of walking legs.
Platyxanthus crenulatus is a species of crab in the family Platyxanthidae. The species is found along the sublittoral zone of the western Atlantic in the waters of Brazil, Uruguay and Argentina, associated mostly with hard bottoms. Adults are robust and conspicuous crabs, with a smooth carapace, dorsally purple and white ventrally. Their claws have marked heterochely and right-handedness, traits associated with shell-breaking feeding habits. Due to its abundance, large size and diet, P. crenulatus presumably has an important ecological role as a predator in benthic communities.
Hirsutodynomene is a genus of crabs in the family Dynomenidae. All species in this genus except the newest one belonged to the genus Dynomene. These two genera form the subfamilia Dynomeninae. The type species of this genus is: Dynomene spinosaRathbun, 1911.
This list of fossil arthropods described in 2016 is a list of new taxa of trilobites, fossil insects, crustaceans, arachnids and other fossil arthropods of every kind that have been described during the year 2016, as well as other significant discoveries and events related to arthropod paleontology that occurred in the year 2016.
Heterosaccus is a genus of barnacles in infraclass Rhizocephala. Like other taxa in this group, they parasitize crabs. Geoffroy Smith circumscribed the genus in 1906; he initially only included H. hians. Smith circumscribed a genus distinct from Sacculina due to a difference of the mesentery; in Heterosaccus, the mesentery does not stretch down to the mantle opening but rather only is present on the ring of attachment.
Tunicotheres is a monotypic genus of crabs in the family Pinnotheridae, and Tunicotheres moseri is the only species in the genus. This crab lives commensally in the atrial chamber of a small ascidian. It is found in the tropical western Atlantic Ocean, the Caribbean Sea and the Gulf of Mexico.
2023 in arthropod paleontology is a list of new arthropod fossil taxa, including arachnids, crustaceans, trilobites, and other arthropods that were announced or described, as well as other significant arthropod paleontological discoveries and events which occurred in 2023.
Xylopaguridae are a family of hermit crabs of the order Decapoda. It was erected in 2016 to accommodate one new genus, Prexylopagurus, and three existing genera that had previously been placed in Paguridae. They occur in the Atlantic, Indian, and Pacific Oceans.
