A revision of the genus Ichnopus (Crustacea: Amphipoda: Lysianassoidea: Uristidae)
The uristid genus Ichnopus is revised and Glycerina included in its synonymy. A key is provided to the world species. Ichnopus pelagicus Schellenberg, I. pseudoserricrus Ledoyer, I. serricrus Walker, I. spinicornis Boeck, I. taurus Costa, (type species), I. tenuicornis (Haswell), I. teretis (Andres) and I. woodmasoni (Giles) are redescribed. The new species I. annasona, I. capricornus, I. caritus, I. comorensis, I. cribensis, I. malpatun, I. parriwi and I. wardi are described. Ichnopus nossibeensis Ledoyer is considered to be a synonym of I. pelagicus. Ichnopus macrobetomma Stebbing is considered to be an unrecognisable species. Two species groups are recognised: the I. spinicornis group, in which the ischium and carpus of gnathopod 1 are long and most species are pelagic, probably micropredators; and the I. taurus group, in which the ischium and carpus of gnathopod 1 are very long and most species are demersal scavengers. Ichnopus is considered to be a tropical to warm temperate Indo-Pacific genus with some remnants in the Mediterranean and the eastern North Atlantic Ocean. The most primitive species in both groups are found in the Mediterranean Sea and the eastern North Atlantic. It appears that the modern genus had its origins in the old Tethyan fauna.