A revision of the genus Alvinocaris Williams and Chace (Crustacea: Decapoda: Caridea: Alvinocarididae), with descriptions of a new genus and a new species of Alvinocaris

The caridean shrimp genus Alvinocaris Williams and Chace, 1982 (Bresilioidea: Alvinocarididae) is revised based upon type material and newly obtained samples from various reducing environments of the deep-sea floor of the world. All species are known from chemosynthetic communities associated with hydrothermal vents, brine or cold seeps. Eight named species are recognized in Alvinocaris, of which one is new, A. dissimilis sp. nov. from the hydrothermally influenced area of Minami-Ensei Knoll, Mid-Okinawa Trough. Alvinocaris dissimilis sp. nov. was confused with A. brevitelsonis in the original description of the latter species by Kikuchi and Hashimoto (2000). Seven previously described species (A. lusca Williams and Chace, 1982, A. markensis Williams, 1988, A. muricola Williams, 1988, A. stactophila Williams, 1988, A. longirostris Kikuchi and Ohta, 1995, A. brevitelsonis Kikuchi and Hashimoto, 2000, and A. williamsi Shank and Martin, 2003) are re-described, and characters distinguishing these species are re-assessed. Two species are confounded in the type series of A. stactophila Williams, 1988. The taxonomic status of the allotype of A. stactophila was not satisfactorily determined, as it appears to be an immature specimen. The geographic range of A. muricola, previously known only from cold seeps on the West Florida Escarpment, Gulf of Mexico, is greatly extended to the Barbados accretionary prism in the tropical western Atlantic and to the newly discovered seeps on the west equatorial African margin (Sibuet et al. 2002). In addition to these eight named species, five indeterminate or unnamed species of Alvinocaris have been reported, and most of them are under study by other authors. A new monotypic genus, Shinkaicaris, is established for Alvinocaris leurokolos Kikuchi and Hashimoto, 2000. The new genus is rather closer to Chorocaris Martin and Hessler, 1990, Opaepele Williams and Dobbs, 1995, and Rimicaris Williams and Rona, 1986 than to Alvinocaris in the structure of the eyes and the armament of the telson and pereopods. A key to aid in the identification of the eight species of Alvinocaris is given, although it is applicable only to adult specimens. The biogeography of Alvinocaris species is discussed.