Holotype ♂ and paratypes 2♀ (IZCAS), CHINA, Guangxi: Chongzuo City, Longzhou County, Shanglong Town, Xinlian Village, Gengyitun, Longmolai Cave, 22°29.809'N, 106°54.103'E, elevation ca. 224 m, 24 July 2011, Xiaoxiao Wang leg.

The specific name derives from the Greek word “oxycerus” = sharp horn, and refers to the sharp cephalic tubercle in the male; noun.

Males of Sinamma oxycera sp. n. can be distinguished from Sinamma sanya (see Lin and Li 2010: 23, figs 19–28) by a long cephalic tubercle (Figs 1G, E), the strongly modified leg I (Figs 2C–E), and the long pyriform palpal bulb (Figs 2A–B). Females can be recognized by a pair of cephalic tubercles (Fig. 1H), a wide, translucent vulval dorsal plate (Fig. 19B), a straight, long, inner vulval plate (Figs 3C, 19B), and the anteriorly wrinkled preanal scutum (Figs 3B, 19B).

Male (holotype). Coloration: body reddish-brown; legs yellowish-brown. Measurements: total length 1.48; carapace 0.68 long, 0.57 wide, 0.57 high; abdomen 0.95 long, 0.71 wide, 0.69 high; clypeus 0.48 high; sternum 0.41 long, 0.41 wide. Length of legs: I 1.89 (0.62, 0.20, 0.42, 0.33, 0.33); II 1.79 (0.57, 0.18, 0.41, 0.30, 0.32); III 1.61 (0.47, 0.16, 0.37, 0.29, 0.32); IV 2.15 (0.66, 0.18, 0.55, 0.40, 0.36).

Carapace (Figs 1A, E, G) finely reticulated, margin rugose; ocular area raised, cephalic tubercle long, sharp (Figs 1G, E); clypeus very high, anterior margin rounded (Figs 1A, G); clypeal area slightly convex; cheliceral horn long, basally wide, distally crooked (Figs 1G, E); sternum with sparse setae, margins rugose (Fig. 1B). Legs: femur I swollen (Fig. 2C); tibiae I–III with 3 trichobothria, tibia IV with 4 trichobothria, and metatarsi I-IV with a thichobothrium; tibia I medially wide, with two small lateral tubercles; metatarsus I with a proximal and a distal tubercle (Figs 2C–E).

Abdomen (Figs 1A–B, E) dorsal scutum oval, finely granulated; ventral scutum reticulated, margin striated; lateral scutum I short; postepigastral scutum exceptionally narrow, subequal in width to preanal scutum (Fig. 1B).

Palp (Figs 2A–B, 16A–B): femur slightly swollen, ventrally granulated; patella approximately 1/2 femur in length; tibia smooth, swollen; bulb long, pyriform, smooth; embolus long, curved slightly, strongly sclerotized; sperm duct extending, visible through the bulbal integument.

Female (paratype). Coloration: same as in male.

Measurements: total length 1.59; carapace 0.68 long, 0.53 wide, 0.41 high; abdomen 1.02 long, 0.84 wide, 0.88 high; clypeus 0.23 high; sternum 0.40 long, 0.39 wide. Length of legs: I 1.89 (0.61, 0.18, 0.46, 0.31, 0.34); II 1.73 (0.55, 0.16, 0.41, 0.29, 0.32); III 1.61 (0.46, 0.15, 0.39, 0.29, 0.31); IV 2.13 (0.64, 0.17, 0.55, 0.39, 0.37).

Carapace (Figs 1C, H and F) with a pair of cephalic tubercles; cephalic part slightly elevated, clypeus lower than in male; cheliceral horn absent. Legs as in male, except for leg I undecorated.

Abdomen (Figs 1C–D, F; 3A): lateral scutum I anteriorly extending beyond the anterior rim of operculum; preanal scutum anteriorly rugose, covered with sparse serrated setae.

Genitalia (Figs 3B–C; 19B): vulval stem transverse, sclerotized; lateral horns robust, supporting the base of vulval ducts; vulval duct narrow, weakly sclerotized; spermathecae translucent, rugose, membranous; vulval dorsal plate wide, fused to lateral horn and base of vulval ducts; inner vulval plate finger-shaped, sclerotized, basally wide; central process absent.

Known only from the type locality (Fig. 22).