Four new species and one newly-recorded species of the genus Opopaea Simon, 1892 (Araneae, Oonopidae) from southern China, with a key to Chinese species

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Introduction
Goblin spiders (Araneae, Oonopidae) are small (usually < 3 mm), six-eyed, haplogyne, non-web building spiders distributed worldwide and are especially diverse in tropical regions.They occupy diverse habitats and mainly occur in leaf litter, under bark and in the tree canopy (Henrard and Jocqué 2012;Ranasinghe and Benjamin 2018).Oonopidae is amongst the nine most diverse spider families with 1940 extant described species in 115 genera (WSC 2024).
The goblin spider genus Opopaea Simon, 1892 is a widespread and highly diverse genus, with biodiversity hotspots in Africa, Asia and Australia (Baehr et al. 2013).A total of 187 valid extant species are currently known, in which 46 in Africa, 35 in Asia, 96 in Australia and New Caledonia and 10 in other areas (WSC 2024).Opopaea are small to medium-sized oonopids, ranging from 1.0 to 2.4 mm in body length, with the abdomen completely covered with ventral and dorsal scuta (Tong and Li 2015).Species of Opopaea have the male palpal patella greatly swollen, connected to the femur medially and the cymbium and bulb are completely fused.The genus Opopaea can be easily distinguished from the other genera by the absence of legs spines, by the completely fused cymbium and bulb and by the presence of dorsolateral, triangular extensions on pedicel, as well as paired scutal ridges on the scuto-pedicel region (Andriamalala and Hormiga 2013;Baehr et al. 2013).
The Opopaea fauna of China is poorly known, with only 18 described species, of which one species (O.media Song & Xu, 1984) is from Anhui and Zhejiang; one species (O. plumula Yin & Wang, 1984) from Hunan; one species (O.sauteri Brignoli, 1974) from Taiwan; two pantropical species (O. apicalis (Simon, 1893), O. deserticola Simon, 1891) from Hainan and Taiwan; six species endemic to Hainan; six species endemic to Yunnan; and one species (O. cornuta Yin & Wang, 1984) widely distributed in southern China (Tong and Li 2010, 2014, 2015).Here, we recognise five species of the genus Opopaea from China, four of which are new to science.

Materials and methods
The specimens were examined using a Leica M205C stereomicroscope.Details of body parts and measurements were studied under an Olympus BX51 compound microscope.Photos were made with a Canon EOS 750D zoom digital camera (18 megapixels) mounted on an Olympus BX51 compound microscope.Endogynes were cleared in lactic acid.Scanning electron microscope images (SEM) were taken under high vacuum with a Hitachi S-4800 after critical-point drying and gold-palladium coating.All measurements in the text are expressed in millimetres.All materials studied are deposited in Shenyang Normal University (SYNU) in Shenyang, China.
Terminology mainly follows Andriamalala and Hormiga (2013) and Tong et al. (2020)  Comment.Opopaea foveolata was originally described from numerous specimens collected throughout Micronesia, including the types from Guam (Roewer 1963).Tong and Li (2010) misidentified this species as Opopaea sauteri Brignoli, 1974, based on specimens collected from Hainan Island.Baehr et al. (2013) re-described this species from numerous specimens collected from Pacific Islands with detailed descriptions and figures.We re-checked the specimens from Hainan, which sufficiently match the description and illustrations of Baehr et al. (2013) to be confident of their identity.
Distribution.Newly recorded from Hainan Island.According to Baehr et al. (2013), this species is widespread in the Pacific Region and is known from many different islands.Etymology.The specific name refers to the type locality and is a noun in apposition.

Opopaea mangun
Diagnosis.This new species is similar to Opopaea macula Tong & Li, 2015 in the large booklung covers and morphology of the scuto-pedical region, but can be distinguished by the acute tip of bulbus (Fig. 6I) vs. round tip (Tong and Li 2015 4A, C, E. Carapace (Fig. 4B, F): oval in dorsal view; sides with longitudinal streaks; median area smooth with rows of setae at lateral edges.Eyes (Fig. 4B, G): ALE largest, PLE smallest; posterior eye row straight viewed from above, procurved from front; ALE separated by less than their radius, ALE-PLE separated by less than ALE radius, PME touching throughout most of their length, PLE-PME separated by less than PME radius.Clypeus height about 1.0 times ALE diameter (Fig. 4G).Sternum (Fig. 4D) longer than wide, fused to carapace; surface smooth; radial furrows present between coxae I-II, II-III and III-IV, with rows of small pits.Abdomen: booklung covers large, ovoid, without setae.Pedicel tube short, ribbed, with small, dorsolateral triangular extensions, scuto-pedicel region lower than pedicel diameter, with straight scutal ridges (Fig. 4H).Palp (Fig. 6A-K): femur slightly shorter than half length of patella and submedially attached to patella; patella strongly enlarged, elongate oval; tibia small, rounded; cymbiobulbus as long as the patella; bulb ventrally straight, tip acute, ventral with prolateral folded ridges (prr).
Distribution.Known only from the type locality.Etymology.The specific name refers to the type locality and is a noun in apposition.
Diagnosis.This new species is similar to Opopaea deserticola Simon, 1892 in the small booklung covers and morphology of the scuto-pedicel region, but can be distinguished by the large needle-like extension of the epigastric region (Fig. 8H) vs. lacking the needle-like extension (Platnick and Dupérré 2009: fig. 32) and the round tip        of distal part of palp (Fig. 9C, I) vs. narrow tip ventrally expanded (Platnick and Dupérré 2009: figs 55, 64).
Distribution.Known only from the type locality.Etymology.The specific name refers to the type locality and is a noun in apposition.