Taxonomic study of the genus Ischnothyreus (Araneae, Oonopidae) from Xishuangbanna Rainforest, southwestern China

Abstract Eight species of the genus Ischnothyreus Simon, 1893 from Xishuangbanna, Yunnan, China are recognized, including six new species: I. cristiformis Tong & Li, sp. nov. (♂♀), I. mangun Tong & Li, sp. nov. (♂♀), I. mengyang Tong & Li, sp. nov. (♂♀), I. peltifer (Simon, 1892), I. qidaoban Tong & Li, sp. nov. (♂♀), I. qiuxing Tong & Li, 2020 (♂♀), I. sijiae Tong & Li, sp. nov. (♀) and I. xiaolongha Tong & Li, sp. nov. (♂♀). The male of I. qiuxing Tong & Li, 2020 is described for the first time. Photos of the habitus and copulatory organs are provided.


Introduction
Oonopidae Simon, 1890 is a diverse spider family with 1872 extant described species in 114 genera. They have a nearly worldwide distribution but are most abundant in the tropics and subtropics (WSC 2021).
Xishuangbanna is a key biogeographic area and a biodiversity hotspot in China (Myers 1988). Spider diversity in this area is high, with 782 species spanning 305 genera in 46 families (Li 2020). The Oonopidae from this region have been poorly studied, with only 2 genera and 10 species recorded so far (Tong andLi 2015a, 2015b;Sun et al. 2019).
Ischnothyreus Simon, 1893 is one of the most speciose genera of the family, with 114 extant species mainly distributed in the Old World (WSC 2021). Up to now, 15 species have been recorded in China (Tong and Li 2008, 2014Tong et al. 2018;Liu et al. 2019). In this paper eight Ischnothyreus species collected from Xishuangbanna are reported. This work presents the first records and descriptions of species in the genus Ischnothyreus from this region.

Materials and methods
The specimens were examined in 95% ethanol using a Leica M205C stereomicroscope. Details were studied with an Olympus BX51 compound microscope. Photos were taken with a Canon EOS 750D zoom digital camera (18 megapixels) mounted on an Olympus BX51 compound microscope. Vulvae were cleared in lactic acid. Scanning electron microscope images (SEM) were taken under high vacuum with a Hitachi TM3030 after critical point drying and gold-palladium coating. All measurements were taken using an Olympus BX51 compound microscope and are given in millimeters in the text. The specimens are preserved in Shenyang Normal University (SYNU) in Shenyang, China.
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. . Legs: pale orange, femur I with 2 prolateral spines, tibia I with 4 pairs, metatarsus I with 2 pairs of long ventral spines. Legs II lost. 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 stout, with numerous lamella-like membranes, retrolateral lobe narrow leaf-shaped (Figs 5, 20D-F).
Etymology. The specific name is a noun in apposition taken from the type locality. Distribution. Known only from the type locality.    Tong & Li, 2020 in the male palp and the large, sclerotized process of male cheliceral fang, but can be distinguished  parts: chelicerae, endites and labium brown; chelicerae straight, base of fangs with large, sclerotized process, fang groove with a few small denticles (Figs 7H-J, 22E, F); anteromedian tip of endites with one strong, tooth-like projection (Fig. 7F). Abdomen: 0.92 long, 0.55 wide; dorsal scutum well sclerotized, pale orange, covering approximately 4/5 of the abdomen length and 3/4 of the abdomen width, not fused to epigastric scutum; epigastric and postgastric scutum well sclerotized, pale orange, fused, postgastric scutum covering about 3/4 of the abdomen length ( Fig.  7A-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 one narrow leafshaped prolateral projection and a distal hook-shaped membrane, retrolateral lobe broad (Figs 8, 20G-I).
Etymology. The specific name is a noun in apposition taken from the type locality. Distribution. Known only from the type locality.

Ischnothyreus sijiae
Male. Unknown. Etymology. The species is named after Miss Sijia Liu, one of the collectors of the holotype.
Comment. Among the known species of the genus Ischnothyreus of China, I. qianlongae Tong &Li, 2008 andI. tergemintus Liu, Xu &Henrard, 2019 are known only from males. I. sijiae sp. nov. can be distinguished from I. tergemintus by the brown colour on the abdomen and sides of carapace (vs yellow abdomen and carapace in   Fig. 16D with Tong and Li (2008: fig. 4A)).

Ischnothyreus xiaolongha
Female (paratype, SYNU-429). Same as male except as noted. Body: habitus as in Fig. 19A surface without external features (Fig. 19H). Endogyne: from the middle of the slightly thickened margin of the postgastric scutum runs a dark, simple winding tube posteriorly, ending in a small bell-shaped atrium (Fig. 24C, D).
Etymology. The specific name is a noun in apposition taken from the type locality. Distribution. Known only from the type locality.