Polychelida

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Polychelida
Temporal range: Upper Triassic–Recent
Stereomastis sculpta
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Malacostraca
Order: Decapoda
Suborder: Pleocyemata
(unranked): Reptantia
Infraorder: Polychelida
Scholtz & Richter, 1995 [1]
Families

Polychelida is an

extant species, all in the family Polychelidae
, and 55 fossil species have been described.

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]

Classification

Polychelida belongs to the group

sister clade to the infraorder Astacidea, which contains the "true" lobsters and crayfish. The cladogram below shows Polychelida's placement within the larger order Decapoda, from analysis by Wolfe et al., 2019.[3]

 Decapoda 
              

Dendrobranchiata (prawns)

Pleocyemata

Stenopodidea (boxer shrimp)

Procarididea

Caridea (true shrimp)

Reptantia

Achelata (spiny lobsters, slipper lobsters)

Polychelida (benthic crustaceans)

Astacidea (lobsters, crayfish)

Axiidea (mud shrimp, ghost shrimp, or burrowing shrimp)

Gebiidea (mud lobsters and mud shrimp)

Anomura (hermit crabs and others)

Brachyura (crabs)

 (crawling / walking decapods) 


The animals grouped into the infraorder Polychelida are united by the presence of at least four pairs of

Upper Triassic,[2] and had its peak diversity in the Mesozoic.[4] Although the extant species are all restricted to deep waters, the group is thought to have originated in shallow water.[4] 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.[4]

References

External links