Diagnosis.--Key characters: Ommatidial size coarse (Fig. 39b); prosternal process not planar and with apex slightly expanded (Fig. 18); mesal antennal spines present (Figs. 8b, 9b); pronotum with impunctate regions present; femoral carinae absent; procoxal cavities open laterally (Fig. 17); lateral projections into mesocoxae from mesosternum absent (Fig. 20); femoral apices rounded (Fig. 26); without dense golden or silver pubescence on elytra; tibial carinae present (Fig. 22); femoral shape clavate (Fig. 37b); elytral sutural spines absent or very weak; lateral antennal spines absent; antennomeres linear, not expanded apically (Fig. 22); elytra with apicolateral spine strong and shifted to apicomedial position; elytra and pronotum with dense vestiture of short pubescence; lateral pronotal tubercles absent; elytral with dark outlining of perimeter as viewed from above. Length: 11-15 mm.
Distribution and Diversity.--Argentina, Brazil, Bolivia, Paraguay, Uruguay. Monotypic.
Discussion.--The implied weighting analysis placed Miopteryx as basal to the clade containing Sphaerion and Mephritus (Figs. 50, 60). More taxa of Sphaerion and Mephritus need to be examined and included in a localized analysis with Miopteryx to determine if it should be placed in one of those genera. I will maintain its status based on this analysis.
Miopteryx differs from examined Mephritus by lacking lateral pronotal tubercles and having a black perimeter of the elytra. Miopteryx differs from Sphaerion species examined in having procoxal cavities open laterally (closed in examined Sphaerion specimens).