Holotype, male (Fig. 84a). Length 2.95 mm. Color of legs and head ferruginous; pronotum and elytron black with bronze lustre. Body in dorsal aspect with marked constriction between pronotum and elytron; in profile dorsally convex. Rostrum in apical half scabrous, coarsely punctate; in basal half with median and pair of submedian ridges; intervening furrows punctate, each with sparse row of erect setae; epistome with transverse, angulate ridge forming distinct median denticle. Pronotum with sides subparallel, anterolaterally rounded to subapical constriction; disk with pair of submedian impressions, coarsely punctate, reticulate; each puncture containing inconspicuous seta; with distinct median ridge. Elytra with humeri swollen, laterally projecting; interval 5 near middle with distinct tubercle dorsally projecting; interval 6 behind middle swollen, gently projecting from lateral outline; striae indistinct; intervals flat, punctate; at base and laterally densely coarsely punctate, remainder less densely punctate. Anteroventral ridge of femora distinct, in meso- and metafemur forming large tooth. Metafemur subapically with stridulatory patch. Dorsal edge of tibiae subbasally with angulation, in mesotibia with blunt tooth. Abdominal ventrite 5 flat, coarsely punctate. Penis (Fig. 84b) with sides of body subparallel; apex subtruncate, weakly angulate; transfer apparatus compact; apodemes 1.6 × as long as body; ductus ejaculatorius without bulbus. Intraspecific variation. Length 2.23–3.06 mm. Female body more slender. Female rostrum dorsally subglabrous, with submedian rows of punctures and sublateral pair of furrows; epistome simple. Female elytra subovate, without tubercles, lateral contour convex.

Holotype (MZB): ARC1510 (EMBL # LM655608), West Nusa Tenggara Prov., Sumbawa, Batu Dulang, Mt. Batu Pasak, sample 2, S08°37.028', E117°15.783', 1305 m, 12-IV-2010. Paratypes (MZB, SMNK, ZSM): West Nusa Tenggara Prov., Sumbawa: 13 exx, ARC1509 (EMBL # LM655607), ARC1511 (EMBL # LM655609), ARC1512 (EMBL # LM655610), same data as holotype; 1 ex, Batu Dulang, Mt. Batu Pasak, sample 3, S08°37.524', E117°15.423', 1385 m, 12-IV-2010; 1 ex, Batu Dulang, Mt. Batu Pasak, sample 3, S08°37.524', E117°15.423', 1385 m, 18-IV-2010; 5 exx, ARC1493 (EMBL # LM655591), ARC1494 (EMBL # LM655592), ARC1495 (EMBL # LM655593), ARC1496 (EMBL # LM655594), Tepal, Pc. Nengas, sample 2, S08°35.884', E117°08.384', 1310 m, 15-IV-2010; 2 exx, Tepal, Pc. Nengas, sample 3, S08°35.386', E117°08.251', 1415 m, 15-IV-2010; 7 exx, Tepal, Pc. Nengas, sample 5, S08°35.740', E117°08.721', 1330 m, 16-IV-2010; 1 ex, Tepal, Pc. Nengas, sample 6, S08°35.533', E117°08.605', 1350 m, 16-IV-2010; 2 exx, Tepal, Pc. Nengas, sample 7, S08°35.176', E117°08.295', 1490 m, 16-IV-2010.

West Nusa Tenggara Prov., Sumbawa (Batu Dulang, Tepal). Elevation: 1305–1490 m.

This epithet is based on the Latin adjective sinuatus (bent) and refers to the elytral outline.

Trigonopterus sinuatus Riedel, sp. n. was coded as “Trigonopterus sp. 333” by Tänzler et al. (2014). Cox1 sequences of the populations from Tepal and Batu Dulang differ 15.7–16.0% p-distance, but morphologically no differences could be found.