Holotype, male (Fig. 83a). Length 3.44 mm. Color of tarsi and antennae ferruginous, remainder black. Body elongate; in dorsal aspect with marked constriction between pronotum and elytron; in profile dorsally with indistinct constriction. Rostrum with median carina terminating on forehead; with pair of submedian ridges; intervening furrows each with row of erect, piliform scales; epistome with transverse, angulate ridge forming minute median denticle. Pronotum without distinct subapical constriction; disk densely punctate, interspaces glabrous; each puncture containing one small scale. Elytra with striae deeply impressed; each with row of narrow, suberect scales; intervals weakly carinate, nude, coriaceous; interval 7 swollen subapically, laterally weakly projecting; apex extended ventrad, beak-shaped. Metafemur with crenulate anteroventral ridge terminating with small tooth; subapically with stridulatory patch and transverse row of denticles. Metatibia in basal half with dorsal edge denticulate. Abdominal ventrite 5 flat, subapically with shallow pit. Penis (Fig. 83b) with body in profile markedly curved ventrad; in dorsal aspect sides basally concave, before apex subparallel; apex medially with small rounded extension; apodemes 1.6 × as long as body; ductus ejaculatorius without bulbus. Intraspecific variation. Length 3.06–3.44 mm. Female rostrum dorsally with pair of lateral furrows, and pair of more shallow submedian furrows; epistome simple. Elytral apex in males rounded, in females narrower, subangulate. Female abdominal ventrite 5 flat. Penis of specimen ARC2747 narrow, sides subparallel from base to shortly before apex.

Holotype (MZB): ARC0281 (EMBL # LM655471), East Sumatra, Lampung Prov., Kalianda, Mt. Rajabasa, sample 1, S05°46.896', E105°37.687', 1281 m, 15-VIII-2006. Paratypes (MZB, SMNK): E-Sumatra, Lampung Prov., Kalianda, Mt. Rajabasa: 1 ex, ARC0282 (EMBL # LM655472), same data as holotype; 2 exx, ARC2746 (EMBL # LM656002), ARC2747 (EMBL # LM656003), sample 1, S05°46.896', E105°37.687', 1281 m, 07-V-2012; 1 ex, sample 6, S05°46.651', E105°37.574', 1257 m, 07-V-2012.

Lampung Prov. (Mt. Rajabasa). Elevation: 1257–1281 m.

This epithet is based on the Latin adjective singularis (alone) and refers to the fact that no other Trigonopterus species could be found on the type locality.

Trigonopterus singularis Riedel, sp. n. was coded as “Trigonopterus sp. 321”.