Trigonopterus allotopus

The beetle is 2.40 mm long. It is black with reddish-brown antennae. The body is ovate and lacks a noticeable constriction between the pronotum and elytron; in profile, it is evenly convex. The rostrum is punctate and slightly wrinkled. The eyes have a furrow along the upper margin that continues into the forehead, which is not ridged.^[1]

The pronotum is mostly smooth, with sparse punctures. The elytra are also mostly smooth, with striae barely visible, marked only by a few deeper punctures near the base and apex. The femora are finely textured and punctate. The metafemur has a ridge along the lower rear edge and a longitudinal groove on the back surface, with a smooth upper rear edge and no stridulatory patch. The mesotibia is rounded at the base and has both an uncus and a larger premucro near the tip. The metatibia has a fringe of curved white setae near the tip, along with an uncus but no premucro. Abdominal ventrite 2 is swollen, with its rear edge projecting and forming a shared cavity with ventrite 1. Ventrite 5 is dull, finely textured, and punctate, with a shallow depression near the tip.^[1]

The penis is short and slender, with nearly parallel sides and a symmetrical apex that ends in a central triangular extension. The transfer apparatus is dentiform and bordered at the tip by a pair of L-shaped sclerites. The ductus ejaculatorius has no distinct bulbus.^[1]

Trigonopterus allotopus is endemic to the island of Sumbawa in the Indonesian province of West Nusa Tenggara, where it is known from near Batu Dulang village on Mount Batu Pasak. It has been recorded from an elevation of 1,305 m (4,281 ft). Specimens of the species were collected from leaf litter, but the beetle is thought to live on foliage based on the behaviour of other closely related species.^[1]