Paralomis is a widely distributed, highly speciose, and morphologically diverse genus 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 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, 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 – 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. 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, 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:
Species Paralomis contains the following species: Image Scientific name Common name Distribution Paralomis aculeata Southwest Indian Ridge Paralomis africana Namibia Paralomis alcockiana Paralomis alis Paralomis anamerae Argentina, Crozet Island, South Georgia Island Paralomis arae Paralomis arethusa Paralomis aspera Paralomis birsteini Southern Ocean near Scott Island Paralomis bouvieri Paralomis ceres Paralomis chilensis Paralomis cristata Paralomis cristulata Paralomis cubensis Paralomis danida Paralomis dawsoni New Caledonia, northern New Zealand, and the Solomon Islands Paralomis debodeorum † New Zealand (Middle–Late Miocene) Paralomis diomedeae Paralomis dofleini Paralomis echidna Paralomis elongata Paralomis erinacea Paralomis formosa Paralomis gowlettholmes Paralomis granulosa False king crab, Chilean snow crab Chile, Argentina, Falkland Islands Paralomis grossmani Paralomis haigae Paralomis hirtella Lau Basin, North Fiji Basin Paralomis histrix Japan (Tokyo Bay to Kyūshū) Paralomis hystrixoides Paralomis inca Paralomis indica Paralomis investigatoris Paralomis jamsteci Paralomis japonica Paralomis kyushupalauensis Paralomis longidactylus Paralomis longipes Paralomis macphersoni Paralomis makarovi Paralomis manningi Deep-sea spider crab West Coast of the United States Paralomis medipacifica Paralomis mendagnai Paralomis microps Paralomis multispina Paralomis nivosa Paralomis ochthodes Indonesia (Gulf of Boni) Paralomis odawarai Paralomis okitoriensis Okinotorishima Paralomis otsuae Paralomis pacifica Paralomis papillata Paralomis papua Paralomis pectinata Paralomis phrixa Paralomis poorei Paralomis roeleveldae Paralomis seagranti Paralomis serrata Paralomis sonne Paralomis spectabilis Eastern Greenland, Iceland Paralomis spinosissima Paralomis staplesi Tasman Fracture, Tonga–Kermadec Ridge Paralomis stella Paralomis stevensi Paralomis taylorae Paralomis truncatispinosa East China Sea, Taiwan Paralomis tuberipes Chile () Paralomis verrilli Paralomis webberi New Zealand Paralomis zealandica Prickly king crab New Zealand
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