Redescription of Phoxocephalopsis Zimmeri With a New Species, and Establishment of the Family Phoxocephalopsidae (Crustacea, Amphipoda) From Magellanic South America

Abstract

The marine fossorial Phoxocephalopsis zimmeri from the shallow sea floor of Magellanic South America is redescribed and made the type genus of a new family. This taxon stands in ancestral position both to the more apomorphic Urohaustoriidae of old and the vastly more apomorphic Haustoriidae confined to the North Atlantic Ocean. Urohaustoriidae have more advanced uropodal rami and Haustoriidae have more advanced mouthparts. A new species, Phoxocephalopsis gallardoi, from Magellan Strait, is described. A key to the species of Phoxocephalopsis includes Phoxocephalopsis deceptionis, P. psammophila, and a supposed new species culled from the literature. The old concept of Haustoriidae has been altered by Bousfield (1965) and Barnard and Drummond (1982) by confining the Haustoriidae to the select group of North Atlantic taxa characterized by Haustorius and by allocating several genera to the Urothoidae. Barnard and Drummond (1982) then described the new families Condukiidae, Urohaustoriidae, and Zobrachoidae from Gondwanan seas and removed the Pontoporeiidae to the superfamily Gammaroidea; the Platyischnopidae were segregated by Barnard and Drummond (1979). Finally another new family, Cheidae, has been described by Thurston (1982). One genus, Phoxocephalopsis, also deserves a family of its own. It stands in a position ancestral perhaps to three of the other haustoriid groups, the Haustoriidae, Urohaustoriidae, and Zobrachoidae. Though it may not be a direct ancestor it is certainly plesiomorphic to Haustoriidae because its mouthparts do not have the apomorphic baler lobes or loss of mandibular lobes on the lower lip and it differs from Urohaustoriidae and Zobrachoidae in the less apomorphic rami of uropods 1 and 2, which are closer to the normal styliform condition of ordinary amphipods than are the linguiform setose rami of the other 2 families. Methods and presentation follow those of Barnard and Clark (1982).