A revised classification and phylogeny of amphipod crustaceans

Abstract

This study analyses the probable origin and evolution of the Amphipoda, a group of small- to medium-sized crustaceans that have diversified in pelagic and benthic habitats of marine, freshwater, and terrestrial environments of the world. The study includes a revision of the suborder Gammaridea based on new concepts of superfamilies and their taxonomic relationships. The classification encompasses some 80 families and 20 superfamilies of which 13 are newly elevated and diagnosed; also formally proposed and diagnosed are the families Urothoidae, Typhlogammaridae, and Gammaroporeiidae and the genus Gam- rnaropoveia. The superfamily revision is based primarily on the morphology of the reproductive male stage, as well as on the plesiomorphic-apomorphic condi- tion of taxonomic characters of the body and appendages previously established at family and superfamily levels of significance. A scheme of probable phylogenetic relationships between amphipod suborders and gammaridean superfamily groups is proposed. The present hypothesis on the probable origin and evolution of the Amphipoda is based partly on the fossil record of amphipods and related malacostracans, on modern distributions of component superfamily groups in relation to geochronology of continental drift and plate tectonics, on pertinent evolutionary models proposed (by others) for other malacostracan groups of comparable distributions and means of dispersal, and on the stimulus to evolution of new animal taxa provided by the proliferation of new plant food resources during the Carboniferous and again in the Cretaceous period. The evidence suggests a late Palaeozoic origin for the Amphipoda, with diversifica- tion maximal during the Mesozoic and continued (in more apomorphic groups) throughout the Cenozoic to the present.