Astacidea


Astacidea is an infraorder of decapod crustaceans including lobsters, crayfish, and their close relatives.

Description

The Astacidea are distinguished from most other decapods by the presence of chelae on each of the first three pairs of pereiopods, the first of which is much larger than the remaining two pairs. The last two pairs of pereiopods are simple, except in Thaumastocheles, where the fifth pereiopod may have "a minute pincer".

Distribution

Members of the infraorder Astacidea are found throughout the world – both in the oceans and in fresh water – except for mainland Africa and parts of Asia.

Classification

Astacidea belongs to the group Reptantia, which consists of the walking/crawling decapods. Astacidea is the sister clade to the infraorder Polychelida, a small group of crustaceans restricted to deep waters. The cladogram below shows Astacidea's placement within the larger order Decapoda, from analysis by Wolfe et al., 2019.
The infraorder Astacidea comprises four extant superfamilies, two of crayfish, one of true lobsters, one of reef lobsters, and a number of fossil taxa., the group contains 782 recognised species, over 400 of which are in the crayfish family Cambaridae. The members of the infraorder Glypheidea were formerly included here.
The cladogram below shows Astacidea's internal relationships and the early split between lobsters and crayfish:

Taxonomy