Hexapodidae is a

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

crab Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the thorax. They live in all the ...

s, the only family in the superfamily Hexapodoidea. It has traditionally been treated as a

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end subfamily botanical names with "-oideae", and zoologi ...

of the family Goneplacidae, and was originally described as a subfamily of

Pinnotheridae The Pinnotheridae are a family of tiny soft-bodied crabs that live commensally in the mantles of certain bivalve molluscs (and the occasional large gastropod mollusc species in genera such as '' Strombus'' and ''Haliotis''). '' Tunicotheres moser ...

. Its members can be distinguished from all other true crabs by the reduction of the

thorax The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the cre ...

, such that only seven sternites are exposed, and only four pairs of

pereiopod The decapod (crustaceans such as a crab, lobster, shrimp or prawn) is made up of 20 body segments grouped into two main body parts: the cephalothorax and the pleon (abdomen). Each segment may possess one pair of appendages, although in various g ...

s are present. Not counting the enlarged pair of

claw A claw is a curved, pointed appendage found at the end of a toe or finger in most amniotes (mammals, reptiles, birds). Some invertebrates such as beetles and spiders have somewhat similar fine, hooked structures at the end of the leg or tarsus ...

s, this leaves only six walking legs, from which the type genus ''Hexapus'', and therefore the whole family, takes its name. Some

anomura Anomura (sometimes Anomala) is a group of Decapoda, 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 (the ...

n "crabs", such as

porcelain crab Porcelain crabs are decapod crustaceans in the widespread family Porcellanidae, which superficially resemble true crabs. They have flattened bodies as an adaptation for living in rock crevices. They are delicate, readily losing limbs when attack ...

s and

king crab King crabs are a taxon of decapod crustaceans chiefly found in cold seas. Because of their large size and the taste of their meat, many species are widely caught and sold as food, the most common being the red king crab (''Paralithodes camtscha ...

s also have only four visible pairs of legs. With the exception of '' Stevea williamsi'', from

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

, all the extant members are found either in the

Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...

oceans, or around the coast of

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

Fossil record

In addition to the extant taxa, the family contains two genera known only from fossils – '' Goniocypoda'' and '' Palaeopinnixa'' – and two further genera include both living and fossil representatives: ''

Hexapus ''Hexapus'' is a genus of crabs in the family Hexapodidae. It contains only three Extant taxon, extant species found in the Indo-West Pacific. They inhabit the intertidal and subtidal areas of shorelines. Description Like other members of the ...

'' and '' Stevea''. The family's fossil record extents back certainly as far as the

Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), E ...

, with unverified reports of a species in the

Maastrichtian The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval from ...

Senegal Senegal,; Wolof: ''Senegaal''; Pulaar: 𞤅𞤫𞤲𞤫𞤺𞤢𞥄𞤤𞤭 (Senegaali); Arabic: السنغال ''As-Sinighal'') officially the Republic of Senegal,; Wolof: ''Réewum Senegaal''; Pulaar : 𞤈𞤫𞤲𞤣𞤢𞥄𞤲𞤣𞤭 � ...

Genera

The following are the

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...

included under Hexapodidae: :Genera marked with are

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

*'' Bellhexapus'' De Angeli, Guinot, & Garassino, 2010 *'' Eohexapus'' De Angeli, Guinot, & Garassino, 2010 *'' Eurohexapus'' De Angeli, Guinot, & Garassino, 2010 *'' Globihexapus'' Schweitzer & Feldmann, 2001 *'' Goniocypoda'' Woodward, 1867 *'' Hexalaughlia'' Guinot, 2006 *'' Hexapinus'' Manning & Holthuis, 1981 *'' Hexaplax'' Doflein, 1904 *''

'' De Haan, 1833 *'' Mariaplax'' Rahayu & Ng, 2014 *'' Lambdophallus'' Alcock, 1900 *'' Latohexapus'' Huang, Hsueh, & Ng, 2002 *'' Paeduma'' Rathbun, 1897 *'' Palaeopinnixa'' Via, 1966 *'' Parahexapus'' Balss, 1922 *'' Pseudohexapus'' Monod, 1956 *'' Rayapinus'' Rahayu & Ng, 2014 *'' Spiroplax'' Manning & Holthuis, 1981 *'' Stevea'' Manning & Holthuis, 1981 *'' Thaumastoplax'' Miers, 1881 *'' Theoxapus'' Rahayu & Ng, 2014 *'' Tritoplax'' Manning & Holthuis, 1981

References

{{Taxonbar, from=Q1061024 Crabs Extant Paleocene first appearances Taxa named by Edward J. Miers Decapod families