| Retroplumidae | |
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| Fossil of Retropluma craverii | |
| Scientific classification | |
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| Superfamily: | Retroplumoidea Gill, 1894 |
| Family: | Retroplumidae Gill, 1894 [1] |
| Synonyms | |
Ptenoplacidae Alcock, 1899 | |
Retroplumidae is a family of heterotrematan crabs, placed in their own (monotypic) superfamily, Retroplumoidea.
Eight genera are recognised, of which all but two are only known from fossils: [2]
Ten species in two genera survive in the deep sea of the Indo-Pacific region: [3]
Fossil specimens ascribed to the Retroplumidae are known from the Late Cretaceous onwards, with Archaeopus antennatus in Coniacian–Maastrichtian rocks in California and Archaeopus ezoensis from Turonian–Maastrichtian rocks from Japan. [4]
The Decapoda or decapods are an order of crustaceans within the class Malacostraca, including many familiar groups, such as crayfish, crabs, lobsters, prawns, and shrimp. Most decapods are scavengers. The order is estimated to contain nearly 15,000 species in around 2,700 genera, with around 3,300 fossil species. Nearly half of these species are crabs, with the shrimp and Anomura including hermit crabs, porcelain crabs, squat lobsters making up the bulk of the remainder. The earliest fossil decapod is the Devonian Palaeopalaemon.
The Stenopodidea or boxer shrimps are a small group of decapod crustaceans. Often confused with shrimp or prawns, they are neither, but belong in a group closer to the reptant decapods, such as lobsters and crabs. They can be easily recognized by their third pereiopod, which is greatly enlarged, while for lobsters and crabs, it is the first pereiopod that is much bigger than the others. There are 71 extant species currently recognized, divided into 12 genera. Three fossil species are also recognized, each belonging to a separate genus. The earliest fossil assigned to the Stenopodidea is Devonostenopus pennsylvaniensis from the Devonian. Until D. pennsylvaniensis was discovered, the oldest known member of the group was Jilinicaris chinensis from the Late Cretaceous.
Calappa is a genus of crabs known commonly as box crabs or shame-faced crabs. The name box crab comes from their distinctly bulky carapace, and the name shame-faced is from anthropomorphising the way the crab's chelae (claws) fold up and cover its face, as if it were hiding its face in shame.
The Ocypodidae are a family of semiterrestrial crabs that includes the ghost crabs and fiddler crabs. They are found on tropical and temperate shorelines around the world.
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.
Maja is a genus of majid crabs erected by Jean-Baptiste Lamarck in 1801. It includes the following extant species:
Cancridae is a family of crabs. It comprises six extant genera, and ten exclusively fossil genera, in two subfamilies:
Dorippoidea is a superfamily of crabs. The earliest fossils attributable to the Dorippoidea date from the Late Cretaceous.
Calappidae is a family of crabs containing 16 genera, of which 7 are only known as fossils:
Dromioidea is a superfamily of crabs mostly found in Madagascar. The earliest fossils attributable to the Dromioidea date from the Late Jurassic.
Hexapodidae is a family of crabs, the only family in the superfamily Hexapodoidea. It has traditionally been treated as a subfamily of the family Goneplacidae, and was originally described as a subfamily of Pinnotheridae. Its members can be distinguished from all other true crabs by the reduction of the thorax, such that only seven sternites are exposed, and only four pairs of pereiopods are present. Not counting the enlarged pair of claws, this leaves only six walking legs, from which the type genus Hexapus, and therefore the whole family, takes its name. Some anomuran "crabs", such as porcelain crabs and king crabs also have only four visible pairs of legs. With the exception of Stevea williamsi, from Mexico, all the extant members are found either in the Indo-Pacific oceans, or around the coast of Africa.
Branchioplax is an extinct genus of crab which existed in Alaska and Washington during the Eocene period. It was first named by Mary Rathbun in 1916, and contains ten species , including Branchioplax washingtoniana from the Hoko River Formation, Branchioplax carmanahensis, and Branchioplax ballingi.
Dakoticancroidea is a superfamily of fossil crabs, containing six species in five genera, divided into two families. The family Dakoticancridae is only known from North American rocks of Late Cretaceous age, while the single species in the Ibericancridae was found in Spain.
Glaessneropsoidea is a superfamily of fossil crabs. They are found in rocks from Late Jurassic age to Late Cretaceous. The 45 species in the superfamily are divided among 11 genera in four families:
Planes is a genus of crabs in the family Grapsidae that currently comprises three extant species: Planes minutus, Planes marinus Rathbun, 1914, and Planes major (=cyaneus). A further fossil species is known from the Middle Miocene of the Caucasus.
Panopeus is a genus of crabs, containing these extant species:
The Galatheoidea are a superfamily of decapod crustaceans comprising the porcelain crabs and some squat lobsters. Squat lobsters within the three families of the superfamily Chirostyloidea are not closely related to the squat lobsters within the Galatheoidea. The fossil record of the superfamily extends back to the Middle Jurassic genus Palaeomunidopsis.
Cyclograpsus is a genus of crabs, containing the following species:
Hyastenus is a genus of crabs in the family Epialtidae, subfamily Pisinae, containing the following extant species:
Mathildellidae is family of crabs belonging to the superfamily Goneplacoidea, containing the following genera:
