This species shares with Mecyclothorax angulosus Perrault the distinctly constricted lateral pronotal margins anterad right, projected hind angles. Both species are also characterized by two supraorbital setae and two dorsal elytral setae, and therefore a setal formula of 2121. Both also display dense transverse-line elytral microsculpture loosely joined in a mesh, the microsculpture resulting in an aeneous reflection. The pronotal median base is more distinctly punctate in Mecyclothorax angulosus, and the cuticle between the punctures is covered with indistinct transverse microsculpture, versus the smooth areas between punctures observed in this new species (Fig. 4D). Elytral stria 6 is shallow and nearly smooth near the elytral midlength in this species, versus deeper and punctate—nearly as deep as striae 1–5—in Mecyclothorax angulosus. Also, elytral striae 2–6 are obsolete basally in this species, versus deep and continuously depressed to their juncture with the elytral basal groove in Mecyclothorax angulosus. Standardized body length in this species is 4.4 mm, larger than Mecyclothorax angulosus at 4.0 mm (n = 2; MNHN holotype male plus CUIC female).