Holotype. China – Xizang Prov. • ♂; glued on a card with two labels as follows: “China: Xizang Prov., Yadong County, Xiayadong, 27°23'48"N, 88°50'02"E, alt. 3000 m, 01.VIII.2021, Peng, Yin & Zhang leg.” “HOLOTYPE: Paederusmirus sp. n., Yang & Peng des. 2024” [red handwritten label]; SNUC. Paratypes. China – Xizang Prov. • 3 ♀♀: Yadong County, Xiayadong, 27°23'48"N, 88°50'02"E, alt. 3000 m, 01.VIII.2021, Peng, Yin & Zhang leg; SNUC • 1 ♀: Yadong County, Xiayadong, 27°23'48"N, 88°50'02"E, alt. 2750 m, 10.VIII.2010, Wen-Xuan Bi leg; SNUC.

Measurements (in mm) and ratios: BL 9.10–9.45, FL 4.42–4.77, HL 1.26–1.32, HW 1.29–1.35, AnL: 3.24–3.78; PL: 1.50–1.57; PW: 1.26–1.29; EL: 1.01–1.09; EW: 1.24–1.27; AW: 1.51–1.59; AL: 0.95; HL/HW: 0.96–0.98; HW/PW: 1.02–1.05; HL/PL: 0.84–0.85; PL/PW: 1.19–1.21; EL/PL: 0.67–0.69; diameter of eye: 0.32–0.33.

Habitus as in Fig. 1B. Coloration: head and abdomen black; antennae light brown; pronotum red; elytra black with faint bluish hue; legs black with dark brown tarsi.

Head (Fig. 1B) weakly transverse, widest across eyes; punctation distinctly coarse and sparse; interstices glossy. Eyes distinctly convex. Antennae distinctly slender, antennomere 4 nearly four times as long as broad and antennomere 10 nearly twice as long as broad. Labrum (Fig. 3A, B) without evident sexual dimorphism, anterior margin in middle with U-shaped median excision, with small projection on either side of median excision. Mandibles (Fig. 3A, B) each with apically bifid molar tooth, without sexual dimorphism.

Pronotum (Fig. 1B) nearly oviform, strongly convex in cross section; punctures sparser and shallower than on head.

Elytra (Fig. 1B) slightly slender, humeral angles obsolete; punctation coarse, well defined, and dense. Hind wings reduced. Metatarsomere I as long as combined length of metatarsomeres II and III.

Abdomen broader than elytra; punctation dense; interstices with shallow microsculpture; posterior margin of tergite VII without palisade fringe; posterior margin of tergite VIII (Fig. 3C, E) weakly convex, shape subject to some variation, but without evident sexual dimorphism.

Male. Sternites III–VI unmodified; sternite VII (Fig. 3F) strongly transverse, with deep median impression without modified pubescence, posterior margin broadly concave; sternite VIII (Fig. 3G) with deep posterior excision, this excision approximately 0.4 times as long as sternite VIII; aedeagus as in Fig. 3H–J and strongly derived; ventral plate nearly truncate; dorsal plate weakly asymmetric, apically bifid and conspicuous; parameres very short; internal sac without sclerotized spine.

Female. Posterior margin of sternite VIII (Fig. 3D) convex.

The species was discovered in two localities situated to southern Yadong, southern Xizang. Some specimens were sifted from moss and leaf litter in montane primary mixed and coniferous forests at an altitude of 3000 m (Fig. 10).

The specific epithet mirus means “strange, wonderful”, referring to the shape of the aedeagus.

Paederusmirus is characterized particularly by the distinctive shape of the aedeagus and additionally by the shape and chaetotaxy of the male sternite VII, as well as by the slender habitus and antennae. Based on the sexual characters, closer affiliations with other Paederus species are not evident.