A phylogeny and classification of the Senticaudata subord. nov. Crustacea: Amphipoda).

The Amphipoda includes a large clade defined by the presence of a previously unrecognised synapomorphy, apical robust setae on the rami of uropods 1-2. We term this clade the Senticaudata subord. nov. (Latin: sentis = thorn). It includes almost all freshwater species as well as a number of marine benthic taxa, formerly part of the 'Gammaridea'. The phylog-eny of the senticaudates was determined by cladistic analysis of morphological characters and character states. Within the suborder Senticaudata there are six infraorders: Carangoliopsida, Talitrida, Hadziida, Corophiida, Bogidiellida and Gam-marida. A classification is provided and all the senticaudate families are diagnosed. We introduce for the first time in am-phipod classification, the level parvorder between infraorder and superfamily. Four new families are described: Kairosidae; Eriopisidae; Nuuanuidae and Kergueleniolidae.