Polychelidae
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The family Polychelidae contains thirty-eight extant species of blind, benthic lobster-like crustaceans. They are found throughout the world's tropical, sub-tropical and temperate oceans, including the Mediterranean Sea and the Irish Sea.[1][2]
Anatomy
The family Polychelidae is notable for the number of chelate (clawed) limbs, with either four or all five pairs of pereiopods bearing claws. This gives rise to the scientific names Polycheles (many-clawed) and Pentacheles (five claws). The first pair of periopods are greatly elongated, but often become broken off while specimens are being brought to the surface. The rostrum is very short or absent, and, although eyestalks are present, the eyes are absent. This family can be seen as evidence of the transition from shrimp-like animals to lobster-like animals, since they possess a number of primitive characters (plesiomorphies), such as the pointed telson, in contrast to the rounded telson in lobsters.[3]
Discovery
Although apparently widespread, and at least locally common, they were first discovered only in the late nineteenth century when they were dredged up by the Challenger expedition from a depth supposed to be "barren, if not of all life, certainly of animals so high in the scale of existence" (Charles Spence Bate). Their kinship with the fossil group Eryonoidea, including well-known genera such as Eryon, was immediately recognised. Since Eryon and its relatives were only known from fossils, lastly in the Jurassic, this made the Polychelidae something of a living fossil.
The reason that polychelids remained unknown for so long is that they live on the sea-floor, often at great depths; the family as a whole has a depth range from less than Script error: No such module "convert". to over Script error: No such module "convert".. This also accounts for the lack of eyesight, since almost none of the sun's light penetrates to such abyssal depths.
Fossil record
A single fossil species is known, Antarcticheles antarcticus, which was found in Jurassic sediments on James Ross Island, close to the Prince Gustav Channel.[4]
Larvae
The larvae of polychelids are very distinctive, and were first described under the name Eryoneicus. Over forty different larval forms are known, although few can be ascribed to known adult species.
Classification
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- Polycheles Heller, 1862Script error: No such module "Check for unknown parameters".
- Polycheles aculeatus Galil, 2000Script error: No such module "Check for unknown parameters".
- Polycheles auriculatus (Bate, 1878)Script error: No such module "Check for unknown parameters".
- Polycheles baccatus Bate, 1878Script error: No such module "Check for unknown parameters".
- Polycheles ceratus Alcock, 1878Script error: No such module "Check for unknown parameters".
- Polycheles coccifer Galil, 2000Script error: No such module "Check for unknown parameters".
- Polycheles enthrix (Bate, 1878)Script error: No such module "Check for unknown parameters".
- Polycheles evexus Galil, 2000Script error: No such module "Check for unknown parameters".
- Polycheles galil Ahyong & Brown, 2002Script error: No such module "Check for unknown parameters".
- Polycheles helleri Bate, 1878Script error: No such module "Check for unknown parameters".
- Polycheles kermadecensis Ahyong and Brown, 2002Script error: No such module "Check for unknown parameters".
- Polycheles nanus (S. I. Smith, 1884)Script error: No such module "Check for unknown parameters".
- Polycheles pacificus (Faxon, 1893)Script error: No such module "Check for unknown parameters".
- Polycheles perarmatus Holthuis, 1952Script error: No such module "Check for unknown parameters".
- Polycheles phosphorus (Alcock, 1894)Script error: No such module "Check for unknown parameters".
- Polycheles politus Galil, 2000Script error: No such module "Check for unknown parameters".
- Polycheles suhmi (Bate, 1878)Script error: No such module "Check for unknown parameters".
- Polycheles surdus Galil, 2000Script error: No such module "Check for unknown parameters".
- Polycheles talismani (Bouvier, 1917)Script error: No such module "Check for unknown parameters".
- Polycheles tanneri Faxon, 1893Script error: No such module "Check for unknown parameters".
- Polycheles trispinosus (De Man, 1905)Script error: No such module "Check for unknown parameters".
- Polycheles typhlops Heller, 1862Script error: No such module "Check for unknown parameters".
- †Antarcticheles Aguirre-Urreta, Buatois, Chernoglasov & Medina, 1990Script error: No such module "Check for unknown parameters".
- †Antarcticheles antarcticus Aguirre-Urreta, Buatois, Chernoglasov & Medina, 1990Script error: No such module "Check for unknown parameters".
- Cardus Galil, 2000Script error: No such module "Check for unknown parameters".
- Cardus crucifer (Thomson, 1873)Script error: No such module "Check for unknown parameters".
- Homeryon Galil, 2000Script error: No such module "Check for unknown parameters".
- Homeryon armarium Galil, 2000Script error: No such module "Check for unknown parameters".
- Homeryon asper (Rathbun, 1906)Script error: No such module "Check for unknown parameters".
- Pentacheles Bate, 1878Script error: No such module "Check for unknown parameters".
- Pentacheles gibbus Alcock, 1894Script error: No such module "Check for unknown parameters".
- Pentacheles laevis Bate, 1878Script error: No such module "Check for unknown parameters".
- Pentacheles obscurus Bate, 1878Script error: No such module "Check for unknown parameters".
- Pentacheles snyderii (Rathbun, 1906)Script error: No such module "Check for unknown parameters".
- Pentacheles validus A. Milne-Edwards, 1880Script error: No such module "Check for unknown parameters".
- Willemoesia Grote, 1873Script error: No such module "Check for unknown parameters".
- Willemoesia forceps A. Milne Edwards, 1880Script error: No such module "Check for unknown parameters".
- Willemoesia inornata Faxon, 1893Script error: No such module "Check for unknown parameters".
- Willemoesia leptodactyla (Willemoes-Suhm, 1875)Script error: No such module "Check for unknown parameters".
- Willemoesia pacifica Sund, 1920Script error: No such module "Check for unknown parameters".
- Template:ExtinctAngusteryon Audo & Furrer, 2020Script error: No such module "Check for unknown parameters".
References
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