A genus-level taxonomic review of primitively segmented spiders (Mesothelae, Liphistiidae) Author Xu, Xin Author Liu, Fengxiang Author Chen, Jian Author Ono, Hirotsugu Author Li, Daiqin Author Kuntner, Matjaz text ZooKeys 2015 488 121 151 http://dx.doi.org/10.3897/zookeys.488.8726 journal article http://dx.doi.org/10.3897/zookeys.488.8726 1313-2970-488-121 3F1CB1995DC645B38B5E65F0AFAFD728 Taxon classification Animalia Araneae Liphistiidae Genus Ryuthela Haupt, 1983 Figures 28-34 Ryuthela Haupt, 1983, type species Heptathela nishihirai Haupt, 1979, P. 286. Diagnosis. Ryuthela males differ from all other Heptathelinae genera by lacking the conductor and by the contrategulum with an enlongate spine (Figures 28, 30). The females differ from Heptathela , Qiongthela , Sinothela , Songthela and Vinathela by one paired receptacular cluster close to each other (Figures 31-32), located at the anterior margin of the bursa copulatrix, and from Ganthela by receptacular clusters without stems that may or may not be fused (Figures 31-34). Description. Total length (excluding chelicerae) = 7-15 mm (N = 151); male palp with denticulate contrategulum and ventral portion with an elongate spine (Figures 28, 30); spinose paracymbium relatively short (Figures 28-30); female genitalia usually with one paired receptacular clusters, except in some specimens, notably in Ryuthela sasakii , where receptacular clusters are unpaired and without stalks (Figures 31-34). Species composition. Ryuthela iheyana Ono, 2002; Ryuthela ishigakiensis Haupt, 1983; Ryuthela nishihirai (Haupt, 1979); Ryuthela sasakii Ono, 1997; Ryuthela tanikawai Ono, 1997. Distribution. Ryukyu Island (Japan). Remarks. In Ryuthela , female genital anatomy shows considerable intraspecific variation, therefore the structure of the male palp appears more reliable for diagnostics and identification.