''Paralomis'' is a widely distributed, highly speciose, and morphologically diverse

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of king crabs in the subfamily Lithodinae.

Description

Like all king crabs, ''Paralomis'' has evolved a crab-like appearance through a process called carcinisation. ''Paralomis'' has either a pentagonal or pyriform carapace. At the very front, its rostrum consists of one short, conical spine projecting forward in the middle and one or more pairs of spines angled upward around the base. Like all king crabs, the gastric region, directly behind the rostrum, is elevated above the others. Like '' Lithodes'' and '' Neolithodes'', the cardiac region – directly behind the gastric region, separated by a deep groove – is triangular. Its three pairs of walking legs – morphologically similar, with the middle pair typically being the longest – are not covered at their bases by the carapace. In adults, the undersides of the dactyli feature horn-like spines. The

abdomen The abdomen (colloquially called the gut, belly, tummy, midriff, tucky, or stomach) is the front part of the torso between the thorax (chest) and pelvis in humans and in other vertebrates. The area occupied by the abdomen is called the abdominal ...

is more calcified than in other king crab genera: the second segment is undivided, the third segment has fused submedian and marginal (outer) plates, and segments three, four, and five are all entirely calcified.

Distribution

''Paralomis'' is present in four of Earth's five oceans – namely the Atlantic, Pacific, Indian, and Southern – as well as all seven continents. They are found from the very shallow intertidal zone to the deep, perpetually dark abyssal zone. The deepest known species of ''Paralomis'' is '' P. bouvieri'', which has been discovered living at .

Taxonomy

''Paralomis'' was described in 1856 by zoologist Adam White and named for its similarity to the genus '' Lomis''. In 1895, marine biologist James Everard Benedict incorrectly placed '' Paralomis granulosa'', the genus'

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

, under the genus '' Lithodes''. Benedict therefore dissolved the genus and created two now-defunct ones – ''Leptolithodes'' and ''Pristopus'' – for other members of ''Paralomis''. ''Paralomis'' is closely related to '' Echidnocerus'', and the monospecific genus '' Glyptolithodes'' – nested cladistically inside ''Paralomis'' – may simply be a species of ''Paralomis''. ''Paralomis'' contains over 70

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

– more than any other king crab genus – and is the most morphologically diverse genus in the subfamily Lithodinae. It contains one fossil species, '' Paralomis debodeorum'', which lived in New Zealand in the Middle–

Late Miocene The Late Miocene (also known as Upper Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch, which lasted from 11.63 Ma (million ye ...

. ''Paralomis'' is distinguished from other king crabs by its abdominal segments: the second is undivided, and the third, fourth, and fifth are entirely calcified. Current scientific consensus is that ''Paralomis'' is

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

, although within this group, carcinologist Shane T. Ahyong in 2010 identified several informal subgroups of ''Paralomis''. ''Paralomis'' relationship to other king crabs can be seen in the following

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

Species

''Paralomis'' contains the following species:

References

External links

* * {{Portal bar, Crustaceans King crabs Decapod genera Taxa named by Adam White (zoologist)