Femorbiona gen. nov., a new genus of sac spiders (Araneae, Clubionidae) from Southeast Asia

Abstract A new genus of Clubionidae Wagner, 1887, Femorbiona Yu & Li, gen. nov., is described, with Clubiona brachyptera Zhu & Chen, 2012 (♂♀; Hainan, China) as the type species. Three species are included in Femorbionagen. nov.: F. brachypteracomb. nov., F. phami Yu & Li, sp. nov. (♂♀; Hai Phong, Vietnam), and F. shenzhen Yu & Li, sp. nov. (♂♀; Guangdong, China).


Introduction
Clubionidae Wagner, 1887 is a relatively large family with 653 valid species distributed worldwide (Li 2020;WSC 2021). More than 80% of the species are currently assigned to the presumptively paraphyletic genus, Clubiona Latreille, 1804 (Marusik and Omelko 2018;Zhang and Yu 2020;Zhang et al. 2021). Deeleman-Reinhold (2001) provided a thorough analysis of the family from Southeast Asia, with eight genera and 57 species. In the same book, she also divided Southeast Asia Clubiona sensu lato into five species groups: C. corticalis group (corresponds to Atalia Thorell, 1887 (FA) and prolateral patellar apophysis (PPA) on the male palp (vs. lacking in Clubiona); male palpal tibia with a ventral apophysis (VTA) but without a retrolateral apophysis (RTA) (vs. VTA absent and RTA well developed in Clubiona); an inflated tegulum (vs. tegulum relatively flat in Clubiona); an indistinct, non-meandering sperm duct (vs. distinct and meandering in Clubiona). Females of Femorbiona gen. nov. differ from those of Clubiona sensu stricto by having tubular spermathecae (vs. subglobular or oval) and shorter copulatory ducts.
The male of Femorbiona gen. nov. also resembles species of the C. corticalis group by the enlarged and protruded tegulum and indistinct sperm duct, but it can be easily distinguished by the femoral and patellar apophyses (Fig. 7) (vs. palpal femur and patella unmodified in corticalis-group species) and the absence of an RTA (vs. present in corticalis-group species). The female of Femorbiona gen. nov. can be easily separated from all corticalis-group species by the posteriorly or centrally located copulatory openings (vs. anteriorly located).
Description. Small to medium sized with body length 2.70-3.79 in males and 2.80-3.99 in females; carapace 1.60-1.70 long in males and 1.39-1.70 in females. Prosoma in profile highest just behind fovea, gradually sloping to pars thoracica, ca. 1.5-1.8 × longer than high; carapace smooth, with short, fine setae, uniformly yellowish brown or yellowish orange, slightly darker anteriorly; fovea short, longitudinal, ca. 2 × diameter of PME. Sternum yellowish, anterior edge truncate, lateral margin with brown extensions fitting intercoxal concavities, posterior region strongly protruded between coxae IV. Female palp without claw, distally with erect, thin, dark bristles. Chelicera uniformly coloured as ocular region, consisting of a coniform base and claw-shaped fang, promargin with more than five teeth, retromargin with more than four teeth. Labium ca. 1.5-1.6 × longer than wide, nearly trapezoidal, concave laterally. Maxillae depressed posteriorly, slightly convergent anteriorly, with dense scopulae on inner margin. Legs uniformly coloured as sternum, with darker femora and coxae I; all femora with four or five dorsal spines; all patellae with none or one dorsal or retrolateral spine; tibiae I-II with two pairs of ventral spines; metatarsi I-II with a pair of spines; tibiae and metatarsi of posterior legs with numerous spines, spination variable on tibiae III-IV and metatarsi III-IV. Leg formula 4213. Abdomen elongate-oval, 1.8-2 × longer than wide, > 2 × longer than high, uniformly coloured. Spinnerets: six, arranged as in all other clubionid spiders. Male palp: femur 2.8-3.2 × longer than wide, retrolaterally with apophysis, usually located proximally, longer or equal to femur diameter; patella modified, with prolateral apophysis, distinctly longer than tibia; tibia cup shaped, slightly wider than long in ventral view, with small, weak ventral apophysis; cymbium oval, ca. 2 × longer than wide; bulb oval, ca 1.6-1.8 × longer than wide; sperm duct indistinct, S-shaped in ventral view, broad part terminating at ca. 1 o'clock position; tegular apophysis absent; conductor small and weakly sclerotised in type species, absent in other species; embolus located prolatero-distally, embedded in tegulum, embolic base an enlarged tubercle, gradually tapered toward apex, embolic tip needle-like or claw shaped. Epigyne with distinct hood, or pocket-like lateral chitinous structures; copulatory openings located posteriorly, separated by 1-4 diameters; spermathecae tubular; bursae oblong, hyaline, much bigger than spermathecae.
Etymology. The generic name is derived from Clubiona and the unique presence of a femoral apophysis on the male palp; feminine in gender.
Comments. There are approximately ten more clubionid species assigned to the Clubiona corticalis group that have palpal and femoral apophyses in males. A review of these species is beyond the scope of this work; however, the following may belong to the new genus:   Diagnosis. Femorbiona brachyptera resembles the species F. phami sp. nov. and F. shenzhen sp. nov. by the general shape of the palp and the endogyne. Males of F. brachyptera can be easily distinguished from the two congeners by the weakly sclerotised conductor (vs. absent) (cf. Fig. 7A and Fig. 7B, C) and the abdomen dorsally marked with numerous brown spots (vs. abdomen without distinct pattern or markings) (cf. Fig. 2E and Figs 4E, 6E). Females of F. brachyptera can be easily recognised by the strongly convoluted dorsal part of the spermathecae, which follows a double S-shaped course (Fig. 2C, D) (vs. moderately convoluted, following an S-shaped course in F. phami sp. nov., as in Fig. 4C, D; not convoluted, following a C-shaped course in F. shenzhen sp. nov., as in Fig. 6C, D).