Two New Species of Psammonyx and the Identity of the Genus Wecomedon (Amphipoda, Gammaridea)

Abstract

Two new species of the genus Psammonyx Bousfield, 1973: P. tzvetkovae sp. nov., and P. kudrjaschovi sp. nov. - are described based on the materials collected from the Sakhalin shelf. Psammonyx tzvetkovae is similar to both Wecomedon similis Jarret and Bousfield, 1982 and P. kurilicus (Gurjanova, 1962). However, it differs from W. similis in having shorter interantennal lobe, more oblique palm of gnathopod 1 and different length of articles 5 and 6 of gnathopod 2. Psammonyx tzvetkovae is distinguished from P. kurilicus in having eyes, the absence of a saddlelike depression on urosomit 1, the shape and armament of article 6 of gnathopods 1 and 2, the absence of a "pineapple pad" on article 5 of gnathopod 2 and other characters. Psammonyx kudrjaschovi is closely related to Hippomedon denticulatus (Bate, 1857) and P. longimerus Jarret and Bousfield, 1982 in having epimeron 3 with a slender, tapering posterodistal tooth, dorsal margin with a distinct notch bearing 1 short seta. But it differs from the former species primarily in a short flagellar article l of antenna l, and is separated from the latter in the presence of "ineapple pad" on article 5 of gnathopod 2, the diagonal keel on epimeron 2, and the wider coxal plate 5. The genus Wecomedon is considered to be synonymous with Psammonyx on the basis of analysis of characters of both genera.