Polychelida

Polychelida is a group of decapod crustaceans. Fossil representatives are known dating from as far back as the Upper Triassic. A total of 38 extant species, all in the family Polychelidae, and 55 fossil species have been described.

Polychelida
Temporal range: Upper Triassic–Recent
Stereomastis sculpta
Scientific classification
Kingdom:
Animalia
Phylum:
Arthropoda
Subphylum:
Crustacea
Class:
Malacostraca
Order:
Decapoda
Suborder:
Pleocyemata
Infraorder:
Polychelida

Scholtz & Richter, 1995 [1]
Families

History

Polychelida had traditionally been included in the infraorder Palinura, alongside the spiny lobsters and slipper lobsters (now in the infraorder Achelata).[1][2] In 1995, Gerhard Scholtz and Stefan Richter of the Freie Universität Berlin carried out a phylogenetic study of the "Reptantia", and concluded that "Palinura" was paraphyletic. They therefore abandoned that taxon and introduced instead the new clade Polychelida.[1]

Membership

The animals grouped into the infraorder Polychelida are united by the presence of at least four pairs of chelae (claws).[3] Five families are included, all but one of which are extinct.[4] The 38 extant species are all in the family Polychelidae.[4] The group has a fossil record stretching back to the Upper Triassic,[2] and had its peak diversity in the Mesozoic.[3] Although the extant species are all restricted to deep waters, the group is thought to have originated in shallow water.[3] Over time, the eyes have reduced in size to the vestigial state seen in extant Polychelidae, the body has narrowed, and the chelae have become less robust; among extant taxa, the most plesiomorphic state is seen in Willemoesia.[3]

Representatives of different families
Cycleryon propinquus (Eryonidae)
Palaeopentacheles roettenbacheri (Palaeopentachelidae)
Proeryon hartmanni (Coleiidae)
Stereomastis sculpta (Polychelidae)
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References
  1. Gerhard Scholtz & Stefan Richter (1995). "Phylogenetic systematics of the reptantian Decapoda (Crustacea, Malacostraca)" (PDF). Zoological Journal of the Linnean Society. 113 (3): 289–328. doi:10.1111/j.1096-3642.1995.tb00936.x.
  2. Hiroaki Karasawa; Fumio Takahashi; Eiji Doi; Hideo Ishida (2003). "First notice of the family Coleiidae Van Straelen (Crustacea: Decapoda: Eryonoidea) from the upper Triassic of Japan" (PDF). Paleontological Research. 7 (4): 357–362. doi:10.2517/prpsj.7.357.
  3. Shane T. Ahyong (2009). "The polychelidan lobsters: phylogeny and systematics (Polychelida: Polychelidae)". In Joel W. Martin; Keith A. Crandall; Darryl L. Felder (eds.). Decapod Crustacean Phylogenetics (PDF). Crustacean Issues. 18. CRC Press. pp. 369–396. ISBN 978-1-4200-9258-5.
  4. Sammy De Grave; N. Dean Pentcheff; Shane T. Ahyong; et al. (2009). "A classification of living and fossil genera of decapod crustaceans" (PDF). Raffles Bulletin of Zoology. Suppl. 21: 1–109.
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