Yunguirius xiannushanensis Wei & Liu 2024, sp. nov.

Yunguirius xiannushanensis Wei & Liu sp. nov. Figs 8, 9, 10, 11 Type material. Holotype ♀ (HBU-WM-24-006): China: Chongqing City, Wulong District, Xiannu Mountain, 29.4508 ° N, 107.7280 ° E, elevation: 1951 m, 15. IX. 2021, T. X. Gu leg. Etymology. The new species is named after the type locality, Xiannu Mountain; an adjective. Diagnosis. The females of Yunguirius xiannushanensis sp. nov. resemble those of Y. ornatus in 1) the atrium is relatively small, less than 1 / 3 the width of the epigyne, with a reduced anterior margin (Fig. 8 A; fig. 3 A in Li et al. 2023); 2) the connection of the copulatory duct and the spermatheca presents dorsally (Fig. 8 B; fig. 3 B in Li et al. 2023). While in other Yunguirius species, the atrium exceeding 1 / 3 the width of the epigyne, with the anterior margin complete (Y. duoge and Y. parvus sp. nov., fig. 2 A; fig. 2 A in Li et al. 2023) or incomplete (Y. subterebratus, Y. terebratus, Y. trigonus sp. nov., Y. wangqiqiae sp. nov. and Y. xiangding, figs 1 A, 4 A, 6 A; fig. 245 A in Zhu et al. 2017; fig. 4 A in Li et al. 2023), and the connection of the copulatory duct and the spermatheca presents ventrally (Figs 1 B, 2 B, 4 B, 6 B; fig. 245 B in Zhu et al. 2017; figs 2 B, 4 B in Li et al. 2023). Y. xiannushanensis sp. nov. can be distinguished from Y. ornatus by the following characteristics: 1) the atrium is pentagonal (Fig. 8 A), versus being trapezoidal in Y. ornatus (Fig. 3 A in Li et al. 2023); 2) the posterior epigynal sclerite is reduced and thin, roughly a quarter of the width of the atrium (Fig. 8 A), versus being more substantial and about equal to the width of atrium in Y. ornatus (Fig. 3 A in Li et al. 2023); 3) the copulatory ducts are folded, and with distinct secondary layer (Fig. 8 B), versus being monolayered in Y. ornatus (Fig. 3 B in Li et al. 2023); 4) the spermathecal bases are large, twice as wide as the stalks, the spermathecal stalks have conch-shaped distal tips, and the spermathecal heads are membranous and only the distal tips are visible (Fig. 8 B); in contrast, in Y. ornatus, the spermathecal bases are relatively small, slightly wider than the stalks, the distal tips of the stalks are normal, and the spermathecal heads are long and sclerotized (Fig. 3 B in Li et al. 2023). Description. Female (holotype) (Fig. 9). Carapace reddish brown. Cervical and radial groove distinct. Cephalic region moderately raised and wide, lateral margin with distinct furrows. Chelicerae with 3 promarginal teeth and 2 retromarginal teeth, condyle red. Sternum longer than wide. Abdomen pale yellow, with 5 chevron-shaped patterns, covered by hairs. Legs red. Total length 13.20. Carapace 6.40 long, 4.25 wide, cephalic region 3.70 wide. Abdomen 7.14 long, 4.36 wide. Eye size and interdistance: AME 0.19, ALE 0.25, PME 0.25, PLE 0.28; AME – AME 0.12, AME – ALE 0.18, AME – PME 0.10, ALE – PLE 0.05, PME – PME 0.13, PME – PLE 0.34. Leg measurements: Leg I 17.18 (2.26, 0.75, 4.27, 1.91, 3.57, 3.20, 1.69), leg II 15.25 (1.94, 0.74, 3.79, 1.70, 3.02, 2.79, 1.67), leg III 12.68 (1.64, 0.79, 3.15, 1.45, 2.10, 2.39, 1.40), leg IV 17.77 (1.94, 0.95, 4.40, 1.88, 3.57, 3.49, 1.70). Epigyne (Fig. 8). Epigynal teeth absent. Atrium relatively small, pentagonal, anterior margin reduced. Epigynal sclerite small, opalescent. Hoods weak, vertically oriented, situated laterally. Fold distinct, triangular. Copulatory ducts broad, laterally originated, folded into 2 layers, and connected with spermathecae ventrally; blind sacs broad and short. Spermathecal base bean-shaped and twice wider than width of spermathecal stalk; spermathecal stalk long, with distal tip conch-shaped; spermathecal head reduced, only remaining a membranous tip on the distal tip of blind sac. Fertilization ducts posteriorly situated. Male. Unknown. Distribution. China (Chongqing). Notes. Our fieldwork indicates that these new Yunguirius species inhabit tube nests with round openings dug into soil, moss, or rotten wood of high humidity, rather than constructing funnel webs beneath rocks or crevices like some other common agelenid spiders. A further study may be required to determine the origins of the burrowing behavior of these spiders.