Quadrisegmentum Hirayama, 1988

Hughes, Lauren Elizabeth & Takeuchi, Ichiro, 2016, Two New Species of Quadrisegmentum (Phtisicidae: Amphipoda: Crustacea) from the Central Indo-Pacific, with Notes on the Type Species Q. triangulum Hirayama, 1988, Records of the Australian Museum 68 (5), pp. 231-244 : 232

Quadrisegmentum Hirayama, 1988

Diagnosis. Head fused (suture absent) with pereonite 1. Antenna 1 well developed; flagellum with more than 2 articles. Antenna 2 well developed; flagellum with more than 2 articles. Mandible well developed; molar absent; palp 3-articulate; article 3 with 1 distal and 1 (or 2) lateral setae. Maxilliped well developed; inner plate (basal endite) larger than outer plate (ischial endite); outer plate (ischial endite) well developed; palp article 3 with distal projection; palp article 4 well developed. Pereonite 4 clavate appendage absent. Pereonites 6 and 7 separated. Pereopod 3 well developed, with 7 articles. Pereopod 4 well developed, with 7 articles. Pereopod 5, with 4 articles, and well-developed dactylus. Pereopods 6 and 7 well developed, with 7 articles. Gills on pereonites 2 to 4. Uropods 2 pairs; Uropod 1 biarticulate, uniramous. Uropod 2 biarticulate, uniramous. Telson dorsal lobe present.

Included species: Quadrisegmentum triangulum Hirayama, 1988 , type species; Q. atauro sp. nov.; Q. lowryi Guerra- García, 2006; Q. yirrgay sp. nov.

Remarks. Characters which define the family Phtisicidae Vassilenko, 1968 are a fully fused head and pereonite 1, absence of a mandibular molar and 3-articulate palp, gills on pereonites 2–4 (3 pair), pereonites 5 and 6 separated and the urosomites 1 and 2 coalesced (see Takeuchi, 1993, 2015; Lim et al., 2012; Takeuchi and Lowry, 2016). The diagnosis of the genus was based observations of the type material of Q. triangulum Hirayama, 1988 by the present study with reference to description and figures of mouth parts in Hirayama (1988) and additionally the two new species described in the current study, Q. atauro sp. nov. and Q. yirrgay sp. nov. (map Fig. 11 ) provides the distribution of the four known Quadrisegmentum species.

Figures

Figure 11. Distribution of world species of Quadrisegmentum Hirayama, 1988.