A new species of Ischnothyreus Simon, 1893 (Araneae, Oonopidae) from Guangdong Province, China

Abstract Background Ischnothyreus Simon, 1893 is one of the most speciose genera of Oonopidae, with 124 extant species mainly distributed in the Old World. Currently, 27 species are known in China. New information A new species, Ischnothyreusruyuanensis Tong, sp. n., is described from Guangdong Province, China. Morphological description and illustrations are provided.


Introduction
With currently 1891 described species in 115 genera, goblin spiders (Oonopidae) are a diverse spider family (WSC 2023). They are small (0.5-4.0 mm), haplogyne, usually sixeyed spiders and are most diverse in the tropical and subtropical regions (Jocqué and Dippenaar-Schoeman 2006).
The genus Ischnothyreus of China have been poorly studied for a long period time. Lee (1966) reported a new recorded species and Brignoli (1974) described one new species from Taiwan. Yin and Wang (1984) described one new species from Yuelu Mountain, Hunan; Xu (1989) described one new species from Anhui; and Hu (2001) Li 2008, Tong andLi 2012), one new species from Taiwan (Tong and Li 2014), one new species from Chongqing (Tong et al. 2018), one new species from Jiangxi (Liu et al. 2019), seven new species and one newly-recorded species from Yunnan (Huang et al. 2021 ) and three new species from Tibet (Tong et al. 2023) have recently been described from China. Up to now, 27 species of Ischnothyreus have been recorded in China.
In this paper, a new species of Ischnothyreus collected from the leaf litter in Guangdong Province of China is described and illustrated.

Materials and methods
All the specimens were collected by sifting leaf litter. The specimens were examined using a Leica M205C stereomicroscope. Details were studied under an Olympus BX51 compound microscope. Photos were made with a Canon EOS 750D zoom digital camera (18 mega pixels) mounted on an Olympus BX51 compound microscope. Vulvae were cleared in lactic acid. Male palps and chelicerae were mounted in Kaiser's glycerol gelatine. 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 in millimetres.
All specimens are preserved in 75% ethanol. The type material is deposited in the College of Life Science, Shenyang Normal University (SYNU) in Liaoning, China.
Female (SYNU-675). Same as male, except as noted. Body: habitus as in Fig

Diagnosis
The new species is similar to I. spineus Tong & Li, 2012 in the thorn-like process on the male chelicerae, but can be distinguished by the thorn-like process nearly straight (Fig.  1H, Fig. 3G and H) vs. strongly curved (see Tong and Li (2012): fig. 3D and H), the sclerotised process of fang base more than 1/3 the whole fangs' length ( Fig. 3G and H) vs. less than 1/4 the whole fangs' length (see Tong and Li (2012): figs. 3H and 5C) and the dark sclerotised ridge (msr) in the middle of the postepigastric scutum (Fig. 2D) vs. a semi-circular depression (see Tong and Li (2012): figs. 4G and 5D).

Etymology
The specific epithet is an adjective referring to the type locality.

Distribution
Known only from the type locality.