Kingdom Animalia Subphylum Crustacea Rank Infraorder | Phylum Arthropoda Higher classification Pleocyemata | |
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Lower classifications Spiny lobster, Slipper lobster | ||
The Achelata is an infra-order of the decapod crustaceans, holding the spiny lobsters, slipper lobsters and their fossil relatives.
Contents
Description
The name "Achelata" derives from the fact that all the members of this group lack the chelae (claws) that are found on almost all other decapods (from the Greek α-, a- = "not", χηλή, chela = "claw"). They are further united by the great enlargement of the first antennae, by the special "phyllosoma" form of the larva, and by a number of other characters.
Classification and fossil record
Achelata contains the spiny lobsters (Palinuridae), the slipper lobsters (Scyllaridae) and the furry lobsters (Synaxidae, now usually included in Palinuridae), as well as two extinct families, Cancrinidae and Tricarinidae.
Both Palinuridae and Scyllaridae have a fossil record extending back to the Cretaceous. The two fossil families contain a single genus each; Tricarina is known from a single Cretaceous fossil, while Cancrinos is known from the Jurassic and Cretaceous. One estimate of the divergence between Achelata and its closest relatives places it at about 341 million years ago.