A key to species of Mucronotus gen. nov.

1. Elytra with large, oval punctures; pronotum glossy, granulate punctures only present on sides of pronotum; processes of trigonium longer than pala; bursal sclerite with transverse bar in anterior portion; females without dimorphic features........................................................................................... M. schwabei (Pic, 1938)

-. Elytra with small, dense punctures; pronotum matt, granulate punctures coarser, absent in the central portion of the pronotal disc; processes of trigonium shorter than pala; bursal sclerite without transverse bar in anterior portion; females with more convex pronotum and unusual setation on pronotal disc.......................................................2.

2. Posterolateral angles of pronotum widely rounded, body covered with long and dense setae...... M. velutinus (Solier, 1849)

-. Posterior angles of pronotum well marked, obtuse to right-angled, setation of body shorter and not so dense [a group of species distinguishable only on the basis of genitalia]...............................................................3.

3. Apices of processes of trigonium widened, armed with denticles on inner sides; anterior portion of bursal sclerite subtrapezoidal............................................................................... M. valdivianus sp. nov.

-. Apices of processes of trigonium gradually narrowing; posterior portion of bursal sclerite different....................4.

4. Each process of trigonium with ca. 15 denticles on its outer margin [females unknown]............ M. patagonicus sp. nov.

-. Each process of trigonium with ca. 30 denticles on its outer margin; anterior portion of bursal sclerite transversely oval..................................................................................... M. enigmaticus sp. nov.