Genus Otacilia Thorell, 1897

Diagnosis. Otacilia can be recognized by the following combination of characters: carapace oval, abruptly narrow anteriorly; labium and endites wider than long; chelicerae each with two bristles (rarely one bristle) on anterior side; leg formula: 4123 (rarely 1423); spination: femora I–II d 0–2, III–IV d 0–1, I pl 3–6, II pl 0–3; tibiae I–II usually with 6–8 pairs of ventral spines; tibia I always with one more rv than pv spine and tibia II always with one more pv than rv spine; metatarsi I–II usually with 3–4 pairs of ventral spines, and always with one more pv than rv spine.

Male palp: femur with ventral apophysis or hump; tibia usually with single pronounced RTA, some species with BTA or DTA; embolus hook-shaped or needle-like, originating antero-prolaterally; tegular apophysis sclerotized or transparent, present or absent, antero-retrolaterally located; conductor membranous, well-developed or absent. Female genitalia: epigynal median plate distinct or absent; vulva with pair of transparent bursae anteriorly and pair of strongly sclerotized spermatheca posteriorly (Jin et al. 2016).

Based on the diagnostic characters of the species-groups identified by Jin et al. (2016), three of the species described here, O. lata sp. nov., O. palmatus sp. nov. and O. rulinensis sp. nov., belong to the ‘ armatissima ’ group, and two new species, O. acerosa sp. nov. and O. xingdoushanensis sp. nov., belong to the ‘ pseudostella ’ group.

The ‘ armatissima ’ group can be diagnosed by: palpal organ with a distinct sclerotized TA or membranous conductor; embolus hook-shaped; epigyne with a distinct median plate without concavity; CO located anteriorly or medially, higher than the spermathecae; CD (the left one in ventral view) anti-clockwise from the CO; connecting tube usually crescent-shaped; spermathecae separated by more than half a spermatheca’s diameter (Jin et al. 2016).

In contrast, the ‘ pseudostella ’ group can be diagnosed by: palpal organ without distinct TA; apophysis present near embolic base (PEA); embolus needle-like; epigyne without median plate, but with a pair of shallow concavities; CO located anteriorly or medially, higher than the spermathecae; spermathecae separated by more than one spermatheca’s diameter (Jin et al. 2016).