Riukiaria Attems 1938

Genus Riukiaria Attems, 1938 Riukiaria Verhoeff, 1936b: 298. Unavailable, because type species was not designated (Jeekel 1971). Rhysolus Chamberlin & Wang, 1953: 8 (with type species: Rhysolus semicirculatus Takakuwa, 1941), synonymized by Hoffman (1980: 157). Sinoria Tanabe, Ishii & Yin, 1996: 13 (with type species: Sinoria tianmu Tanabe, Ishii & Yin, 1996), synonymized by Golovatch (2014: 189). Parariukiaria Nguyen, 2016: 332 (with type species: Parariukiaria cucfuongensis Nguyen, 2016), synonymized by Golovatch (2023: 233). Riukiaria – Attems 1938: 151. — Shinohara 1977: 117–119. — Korsós et al. 2011: 56, fig. 1. — Golovatch 2023: 233–234. Type species Riukiaria pugionifera Verhoeff, 1936b: 298–299, figs 1–2 (designated by Attems 1938), “Riukiu-Insel Okinawa ”. Diagnosis Xystodesmid typically of length over 30 mm, up to 80 mm, colouration generally dark grey, brown, metallic green, or uniformly light yellow, orange, or with distinct bands and patches on each ring; paranota also dark or with large yellow or white spots in their entire edge (vs Xystodesmus with smaller body size, and colouration with small red, orange or yellow paranotal spots). Gonopods with two branches, prefemoral process and acropodite form a simple forceps (Korsós et al. 2011), sometimes with different teeth or additional small processes. According to Golovatch (2023: 233): “Morphologically, Riukiaria differs from Xystodesmus in the less elaborate and largely forceps-shaped gonopodal telopodite, in which among the two main branches, the solenomere and prefemoral process, the former is always longer to much longer than the latter, if any, while the gap between both is very considerable. In contrast, the solenomere and prefemoral process in Xystodesmus are quite variable in length and shape, both lying clearly adjacent and/or clearly appressed to each other, forming no considerable gap between them.” The genus encompasses 37 species (Korsós et al. 2011; Golovatch 2023), with a wide distribution including the central and southern Japanese islands, Taiwan, central-east China, and North Vietnam. Only one species was briefly mentioned from South Korea (Takakuwa 1941b), but its occurrence has remained unconfirmed up to now.