Lectotype male designated herein in order to fix the status of the name-bearing specimen: (barely legible green disk) “N[?], Mecistost. pilifer, Amazones, Bates, ’69[5?]” / “TYPE” / “MUSEUM PARIS, COLL DE MARSEUL 1890” / “LECTOTYPE” / “Mecistostethus pilifer Marseul, 1870 Lectotype N. DÉGALLIER” / “LECTOTYPE Mecistostethus pilifer Marseul, M.S. Caterino & A.K. Tishechkin des. 2010”; MNHN.

Small, length 1.9mm, width 1.5mm;frontal stria/carina complete; frons and epistoma with microsculpture; anterior pronotal stria short, weak, barely divergent from margin (Fig. 3C); pronotum with >10 discal setae (despite many evidently broken off of type), with several scattered setae in addition to well-defined submarginal row (Fig. 3C); pronotal microsculpture gradually more conspicuous to front and sides, inconspicuous at base; lateral pronotal punctures absent (aside from setigerous punctures); prosternal striae absent (Fig. 4B); metaventral stria interrupted at middle (Fig. 4B); elytral microsculpture extremely faint, visible only near apex; elytra with stria 1 complete, bearing numerous setae, stria 2 barely abbreviated at base; aedeagus (Fig. 6C) relatively short, with sides rounded, almost evenly tapering basally and apically; tegmen quite flat, with apex only very weakly curved ventrad (Fig. 6D); basoventral concavity shallow but well defined, with basolateral carinae and fine ventral keel present; median lobe slightly over half tegmen length.

This species is known only from the vague type locality: “Amazones”.