Pilumnoidea 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, whose members were previously included in the Xanthoidea

Xanthoidea

Xanthoidea is a superfamily of crabs, comprising the three families Xanthidae, Panopeidae and Pseudorhombilidae. Formerly, a number of other families were included in Xanthoidea, but many of these have since been removed to other superfamilies. These include Carpilioidea, Eriphioidea, Hexapodoidea,...

. The three families are unified by the free articulation

Joint

A joint is the location at which two or more bones make contact. They are constructed to allow movement and provide mechanical support, and are classified structurally and functionally.-Classification:...

 of all the segments of the male crab's abdomen

Abdomen

In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...

 and by the form of the gonopods. The Cretaceous

Cretaceous

The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

 genus Titanocarcinus is believed to belong to the Pilumnidae; apart from Titanocarcinus, the earliest fossils assigned to this group are of Eocene

Eocene

The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...

 age.

Classification

Pilumnidae is by far the largest of the three families, with 73 of the 78 genera:
Pilumnidae Samouelle, 1819

• Subfamily Calmaniinae Števčić, 1991
  • Calmania Laurie, 1906
• Subfamily Pilumninae Samouelle, 1819
  • Actumnus
    Actumnus
    Actumnus is an genus of crabs in the family Pilumnidae. Alongside the 28 extant species, it has a fossil record extending back into the Miocene.-Species:Actumnus contains 28 extant species:*Actumnus amirantensis Rathbun, 1911...
    
    Dana, 1851
  • Aniptumnus Ng, 2002
  • Bathypilumnus Ng & L. W. H. Tan, 1984
  • Benthopanope Davie, 1989
  • Budapanopeus † Müller & Collins, 1991
  • Cryptopilumnus Hsueh, Huang & Ng, 2009
  • Danielum Vázquez-Bader & Gracia, 1995
  • Eohalimede † Blow & Manning, 1996
  • Eopilumnus † Beschin et al., 2002
  • Eumorphactaea † Bittner, 1875
  • Eurycarcinus A. Milne-Edwards, 1867
  • Galenopsis † A. Milne-Edwards, 1865
  • Glabropilumnus Balss, 1932
  • Gorgonariana Galil & Takeda, 1988
  • Heteropanope Stimpson, 1858
  • Heteropilumnus De Man, 1895
  • Latopilumnus Türkay & Schuhmacher, 1985
  • Lentilumnus Galil & Takeda, 1988
  • Lobogalenopsis † Müller & Collins, 1991
  • Lobopilumnus A. Milne-Edwards, 1880
  • Lophopilumnus Miers, 1886
  • Nanopilumnus Takeda, 1974
  • Neoactumnus T. Sakai, 1965
  • Parapleurophrycoides Nobili, 1906
  • Pilumnopeus A. Milne-Edwards, 1867
  • Pilumnus Leach, 1816
  • Priapipilumnus Davie, 1989
  • Pseudactumnus Balss, 1933
  • Serenepilumnus Türkay & Schuhmacher, 1985
  • Serenolumnus Galil & Takeda, 1988
  • Takedana Davie, 1989
  • Viaderiana Ward, 1942
  • Xestopilumnus Ng & Dai, 1997
  • Xlumnus Galil & Takeda, 1988
• Subfamily Eumedoninae Dana, 1853
  • Ceratocarcinus Adams & White in White, 1847
  • Echinoecus
    Echinoecus
    Echinoecus is a genus of crabs that live in association with sea urchins. Formerly considered monotypic, the genus is now thought to contain three species:...
    
    Rathbun, 1894
  • Eumedonus H. Milne Edwards, 1837
  • Gonatonotus Adams & White, in White, 1847
  • Hapalonotus Rathbun, 1897
  • Harrovia Adams & White, 1849
  • Permanotus D. G. B. Chia & Ng, 1998
  • Rhabdonotus Milne-Edwards, 1879
  • Santeella † Blow & Manning, 1996
  • Tauropus D. G. B. Chia & Ng, 1998
  • Tiaramedon D. G. B. Chia & Ng, 1998
  • Viacarcinus † Blow & Manning, 1996
  • Zebrida White, 1847
  • Zebridonus D. G. B. Chia, Ng & Castro, 1995
• Subfamily Rhizopinae Stimpson, 1858
  • Caecopilumnus Borradaile, 1902
  • Camptoplax Miers, 1884
  • Ceratoplax Stimpson, 1858
  • Cryptocoeloma Miers, 1884
  • Cryptolutea Ward, 1936
  • Itampolus Serène & Peyrot-Clausade, 1977
  • Lophoplax Tesch, 1918
  • Luteocarcinus Ng, 1990
  • Mertonia Laurie, 1906
  • Paranotonyx Nobili, 1905
  • Paraselwynia Tesch, 1918
  • Peleianus Serène, 1971
  • Pronotonyx Ward, 1936
  • Rhizopa Stimpson, 1858
  • Pseudocryptocoeloma Ward, 1936
  • Pseudolitochira Ward, 1942
  • Rhizopoides Ng, 1987
  • Selwynia Borradaile, 1903
  • Ser Rathbun, 1931
  • Typhlocarcinops Rathbun, 1909
  • Typhlocarcinus Stimpson, 1858
  • Zehntneria Takeda, 1972
• Subfamily Xenopthalmodinae Števčić, 2005
  • Arges † De Haan, 1835
  • Xenopthalmodes Richters, 1880

Galenidae Alcock, 1898

• Dentoxanthus Stephensen, 1946
• Galene De Haan, 1833
• Halimede De Haan, 1835
• Parapanope De Man, 1895

Tanaocheleidae

Tanaocheles

Tanaocheles is a genus of crabs, the only genus in the family Tanaocheleidae. It contains two species, T. bidentata and T. stenochilus...

 Ng & P. F. Clark, 2000

• Tanaocheles
  Tanaocheles
  Tanaocheles is a genus of crabs, the only genus in the family Tanaocheleidae. It contains two species, T. bidentata and T. stenochilus...
  
  Kropp, 1984