﻿Three new species of the genus Ischnothyreus Simon, 1893 and the discovery of the male of I.linzhiensis Hu, 2001 from Tibet, China (Araneae, Oonopidae)

﻿Abstract Four species of the genus Ischnothyreus Simon, 1893 from Tibet, China are recognised, including three new species, I.caoqiisp. nov. (female), I.metoksp. nov. (female), and I.pomesp. nov. (male and female). Males of Ischnothyreuslinzhiensis Hu, 2001 are discovered for the first time since its description. Descriptions, diagnoses, and photographs of the four species are provided.


Introduction
Oonopidae is a diverse spider family with 1888 extant described species in 115 genera (WSC 2023). They have a nearly worldwide distribution, occurring mainly in the leaf litter, under bark, and in the tree canopy (Jocqué and Dippenaar-Schoeman 2006;Ubick and Dupérré 2017). The genus Ischnothyreus Simon, 1893 is one of the most speciose genera of Oonopidae, with 121 extant species mainly distributed in the Old World (WSC 2023).
The oonopid spiders of Tibet have been poorly studied. Hu (2001) reported two new species from Nyingchi, Tibet, i.e., Gamasomorpha linzhiensis Hu, 2001, and Ischnothyreus linzhiensis Hu, 2001. Cheng et al. (2021 reported one new genus and two new species from Nyingchi, Tibet, i.e., Paramolotra pome , and Paramolotra metok  In this paper three new species of the genus Ischnothyreus, collected from Tibet, are reported and a detailed re-description of I. linzhiensis Hu, 2001 is provided including the first male.

Materials and methods
The specimens were examined using a Leica M205C stereomicroscope. Details were studied under an Olympus BX51 compound microscope. Vulvae were cleared in lactic acid. Photomicroscope images were made with a Canon EOS 750D zoom digital camera (18 megapixels) mounted on an Olympus BX51 compound microscope. Photos were stacked with Helicon Focus 6.7.1 and processed in Adobe Photoshop CC 2020. For scanning electron microscopy (SEM), specimens were air-dried, sputter-coated using IXRF SYSTEMS, and imaged with a Hitachi TM3030 SEM. All measurements were taken using an Olympus BX51 compound microscope and are in millimeters. All specimens are preserved in 75% ethanol. The type material is deposited in Shenyang Normal University (SYNU) in Shenyang, China.

Diagnosis.
The new species is similar to I. jianglangi Tong & Li, 2020 in the size of the abdominal scuta, but can be distinguished by the large, semicirculared structure of the endogyne and the simple winding duct (Fig. 1H, I) vs. a triangular structure and a complex winding duct (see Tong et al. 2020: fig. 17A, B).
Male. Unknown. Etymology. The species is named after Mr. Qi Cao, the collector of the type specimens; noun in genitive case.
Distribution. Known only from the type locality. Description. Male (SYNU-509). Body: habitus as in Fig. 2A-C; body length 1.64. Carapace: 0.88 long, 0.65 wide; yellow, oval in dorsal view, pars cephalica strongly elevated in lateral view, surface of elevated portion of pars cephalica smooth, sides finely reticulate, lateral margin straight, smooth (Fig. 2G). Clypeus: straight in frontal view, ALE separated from edge of carapace by their diameter (Fig. 2I). Eyes: ALE largest, ALE circular, PME squared, PLE oval; posterior eye row recurved from   above; ALE touching, ALE-PLE touching (Fig. 2G, I). Sternum: as long as wide, pale orange (Fig. 2H). Mouthparts: chelicerae, endites and labium yellow; chelicerae straight, anterior face with conical apophysis, base of fangs with large flag-like sclerotized process, fang groove with a few small and one larger denticles (Figs 2D-F, 3C); anteromedian tip of endites with one strong, tooth-like projection (Fig. 2H). Abdomen: 0.76 long, 0.44 wide; dorsal scutum dark brown, covering 4/5 of abdomen width and approximately 5/6 of abdomen length, not fused to epigastric scutum; postgastric scutum covering ~ 2/3 of abdomen length. Legs: pale orange, femur I with two prolateral spines, tibia I with four pairs, metatarsus I with two pairs of long ventral spines. Leg II spination similar to leg I, except femur with only one prolateral spine. Legs III and IV spineless. Palp: trochanter with ventral projection; bulb with one ventral protuberance, distal end of bulb stout, with dorsal membrane, needle-like membrane and two leaf-like projections (Figs 2J-L, 4A, B).
Distribution. China (Tibet: Nyingchi).  Edward & Harvey, 2014 in the size of the abdominal scuta, but can be distinguished by the semicircle-shaped depression of the endogyne (Fig. 5H) vs. a smile-shaped depression (see Edward and Harvey 2014: figs 13I, 14F).
Male. Unknown. 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 having the large, chestnut-shaped structure of the endogyne, but can be distinguished by the simple winding duct of the endogyne (Fig. 7H, I) vs. the complex winding duct (see Tong et al. 2020: fig. 17B). Males of the new species are similar to those of I. yunlong  in having the large flag-like sclerotized process of the cheliceral fang, but can be distinguished by the fused abdominal dorsal and epigastric scuta (Fig. 6C) vs. unfused (see Huang et al. 2021: fig. 1E), and by lacking the dorsal protuberance on the distal end of the bulb (Fig. 4D, E) vs. with dorsal protuberance (see Huang et al. 2021: fig. 2J).
Etymology. The specific name is a noun in apposition taken from the type locality. Distribution. Known only from the type locality.