Taxonomic study of the genus Ischnothyreus (Araneae, Oonopidae) from Xishuangbanna Rainforest, southwestern China Author Tong, Yanfeng https://orcid.org/0000-0002-4348-7029 Life Science College, Shenyang Normal University, Shenyang 110034, China Author Sun, Xiaochen Life Science College, Shenyang Normal University, Shenyang 110034, China Author Li, Shuqiang https://orcid.org/0000-0002-3290-5416 Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China lisq@ioz.ac.cn Author Bian, Dongju CAS Key Laboratory of Forest Ecology and Management, Institute of Applied Ecology, Shenyang 110016, China biandongju@163.com text ZooKeys 2021 2021-04-26 1034 165 197 http://dx.doi.org/10.3897/zookeys.1034.63388 journal article http://dx.doi.org/10.3897/zookeys.1034.63388 1313-2970-1034-165 B93166004BE645879BB124B575FD405B B10A957A0D455B8F81DAD0409B37F8F5 Ischnothyreus cristiformis Tong & Li sp. nov. Figures 1 , 2 , 3 , 20A-C , 22A, B , 23A, B Type material. Holotype ♂: China, Yunnan, Mengla County, Xiaolongha, Xishuangbanna Biodiversity Conservation Corridor, montane monsoon forest; 21°24.161'N , 101°36.412'E ; 791 m; 16.VI.2013; Q. Zhao and Z. Chen leg. (SYNU-379). Paratypes. 1♀: same data as for holotype (SYNU-380); 3♂1♀: Xiaolongha, Xishuangbanna Biodiversity Conservation Corridor, Qidaoban, valley forest; 21°24.808'N , 101°37.874'E ; 711 m; 18.VI.2013; Q. Zhao and Z. Chen leg. (SYNU-381-384). Diagnosis. The new species is similar to I. mangun sp. nov. and I. xiaolongha sp. nov. by the lamella-like membrane of the male palp and short dorsal abdominal scutum, but can be distinguished by the large cockscomb-shaped sclerotized process (Fig. 1H-J ) of the male cheliceral fang (vs the unmodified cheliceral fang (Fig. 4H, I ) in I. mangun sp. nov. and the tongue-shaped sclerotized process (Fig. 17H-J ) in I. xiaolongha sp. nov.), the broad rectangular-shaped retrolateral lobe of the bulb (Fig. 2F ) (vs the leaf-shaped lobe (Figs 5F , 18F ) in I. mangun sp. nov. and I. xiaolongha sp. nov.). The female differs from I. mangun sp. nov. and I. xiaolongha sp. nov. by the large bowl-shaped atrium (Fig. 3H ) (vs small rectangular-shaped atrium (Fig. 6F ) in I. mangun sp. nov. and small bell-shaped atrium (Fig. 19H ) in I. xiaolongha sp. nov.). Figure 1. Ischnothyreus cristiformis sp. nov., male holotype A-C habitus, dorsal, lateral and ventral views D-G prosoma, dorsal, lateral, ventral and anterior views H-J left chelicerae, anterior, posterior and lateral views. Abbreviation: stp = strong, tooth-like projection. Scale bars: 0.4 mm ( A-G ); 0.1 mm ( H-J ). Description. Male (holotype). Body : habitus as in Fig. 1A-C ; body length 1.64. Carapace : 0.88 long, 0.65 wide; yellow, with egg-shaped patches behind eyes, surface of elevated portion of pars cephalica smooth, sides finely reticulate, lateral margin straight, smooth (Fig. 1D, E ). Clypeus : height about 2/3 of ALE diameter (Fig. 1G ). Eyes : see Fig. 1D, G . Sternum : pale orange (Fig. 1F ). Mouthparts : chelicerae, endites and labium orange; chelicerae straight, base of fangs with large cockscomb-shaped sclerotized process, fang groove with a few small denticles (Figs 1H-J , 22A, B ); anteromedian tip of endites with one strong, tooth-like projection (Fig. 1F ). Abdomen : 0.76 long, 0.44 wide; dorsal scutum well sclerotized, pale orange, covering 1/3 of the abdomen width and approximately 2/3 of the abdomen length, fused to epigastric scutum; epigastric and postgastric scute well sclerotized, pale orange, fused, postgastric scutum covering about 2/3 of the abdomen length (Fig. 1A-C ). Legs : pale orange, femur I with 2 prolateral spines, tibia I with 4 pairs, metatarsus I with 2 pairs of long ventral spines. Leg II spination similar to leg I except femur with only 1 prolateral spine. Legs III and IV spineless. Palp : trochanter with ventral projection, cymbium brown; bulb with 2 ventral protuberances, one large and another very small, distal end of bulb elongated, with numerous lamella-like membranes, retrolateral lobe broad, rectangular-shaped (Figs 2 , 20A-C ). Figure 2. Ischnothyreus cristiformis sp. nov., male holotype, left palp, SEM A-C prolateral, retrolateral and dorsal views D, E palpal bulb, prolateral and retrolateral views F-H distal part of palpal bulb, dorsal, prolateral and retrolateral views. Abbreviations: llm = lamella-like membrane; rl = retrolateral lobe; rol = round lobe; tsm = thread-shaped membrane; vpr = ventral protuberance. Female (paratype, SYNU-380). Same as male except as noted. Body : habitus as in Fig. 3A-C ; body length 1.76. Carapace : 0.72 long, 0.67 wide. Mouthparts : chelicerae and endites unmodified. Abdomen : 1.05 long, 0.67 wide; dorsal scutum covering 1/3 of the abdomen length, about 1/4 of the abdomen width. Epigastric area : postgastric scutum with strongly sclerotized structure in the middle (Fig. 3H ). Endogyne : from the middle of the slightly thickened margin of the postgastric scutum runs a dark, simple winding tube, ending in a large bowl-shaped atrium (Fig. 23A, B ). Etymology. The specific name is a Latin adjective and refers to the large cockscomb-shaped sclerotized process of the cheliceral fang. Distribution. Known only from the localities of the type series. Figure 3. Ischnothyreus cristiformis sp. nov., female paratype A-C habitus, dorsal, lateral and ventral views D-G prosoma, dorsal, lateral, ventral and anterior views H epigastric region, ventral view. Abbreviation: css = central strongly sclerotized structure; Scale bars: 0.4 mm ( A-G ); 0.2 mm ( H ).