Revision of the crustacean amphipod genus Jassa Leach (Corophioidea: Ischyroceridae)

Abstract

The crustacean amphipod genus Jassa is revised to encompass the type species J. falcata (Montagu, 1808), the previously recognized species J. ingens (Pfeffer, 1888), J. herdmani (Walker, 1893), J. pusilla (G. O. Sars, 1894), and J. marmorata Holmes, 1903, and the new species J. alonsoae, J. borowskyae, J. carltoni, J. fenwicki, J. gruneri, J. hartmannae, J. justi, J. morinoi, J. myersi, J. oclairi, J. shawi, J. slatteryi, J. staudei, and J. thurstoni. Jassa odontonyx (G. O. Sars, 1894) is synonymized with J. pusilla, and J. pulchella Leach, 1814 is confirmed as synonymous with J. falcata. Jassa wandeli Chevreux, 1906, J. multidentata Schellenberg, 1931, J. goniamera Walker, 1903, J. barnardi Stephensen, 1949, J. lilipuna J. L. Barnard, 1970, and J. ocia (Bate, 1862) will be assigned to other genera. The nomenclatural disposition of other species that were at one time assigned to the genus Jassa is also given. The genus Jassa can be distinguished from its closest relatives by the following key characters: the outer rami of the third uropods are tipped by a pair of cusps and a basally immersed, dorsally recurved spine; the palms of the first and second gnathopods are defined by a cluster of three spines; at the last molt the male produces a thumb-like protuberance on the propodus of the second gnathopods by incision of the palm anterior to the palm-defining spines; and thumbed males have dimorphic second gnathopods.