Holotype: NMB, 1♂; ARGENTINA, Salta, Salta (Cerro San Bernardo), 8.ii.1982, 1450 m, H & A Howden.

Paratypes: MZSP 7062; 1♀; ARGENTINA, Salta, i.1949, Wigodzinsky. - NMB; 1♀ Amblayo, ii.1945.

Diagnosis: Paramaronius unituberculatus sp. nov. is characterized by the single apical tubercle in the elytra of males and by the shapes of aedeagus and the seventh ventrite of males and females.

Etymology: The specific epithet is a derivative of the Latin words uni (one) + tuberculatum (tuberculate), referring to the single tubercle on the apex of each elytron.

Description: Head occipital region, center of clypeus and apex of mandibles light to dark brown; vertex, frons, sides of clypeus, genae and base of mandibles pale yellow; antennae light to dark brown, lighter on ventral side of three proximal antennomeres. Labial and maxillary palpi light brown, darker on last palpomeres. Pronotum pale yellow with two large dark brown lateral patches. Scutellum pale yellow. Elytra dark brown with yellow apical patch. Hind wings dark brown. Thorax and legs light brown, darker on the dorsal surface of femora and pro- and mesothoracic tarsi. Abdomen dark brown, yellow on the margins of each ventrite and tergite; last ventrite completely brown.

Male (Fig. 1): head densely pubescent; vertex and occipital region flat, lateral margins slightly arcuate behind the eyes. Antennae long, with two antennomeres surpassing the apex of elytra; antennomere I slightly swollen apically, antennomere II three times shorter than I, antennomere III twice longer than II, antennomeres IV-VIII subequal in length, slightly longer than I, antennomeres VIII-XI progressively decreasing in length towards the apex. Pronotum as long as wide; anterior and posterior margins rounded; lateral margins slightly sinuate; anterior and posterior angles directed upwards. Scutellum triangular, apex widely rounded. Elytra (Fig. 3) densely pubescent, short, each elytron 2.6 times longer than wide; internal margins dehiscent from apical half, apex rounded; each elytron with a deep and broad hollow meeting medially; a dense fringe of long setae on the anterior wall and margin of hollows; dorsal surface with a large apical tubercle. Legs slender; tibiae longer than femora; tarsomeres gradually increasing in size from pro- to metathoracic leg; first metatarsomere 1.85 times longer than second and 3.65 times longer than third. Abdomen: abdominal glandular pores slightly prominent. Seventh abdominal ventrite (Fig. 9) slightly wider than long, pubescent, distal margin slightly emarginated laterally and strongly emarginated and rounded at middle. Aedeagus (Fig. 5–8) with a large right prolongation of tegmen, broadly sinuous on posterior margin, covered with long and thick setae; base and dorsal surface with projecting apophysis; left setiferous prolongation long and curved, slightly clubbed, with few setae at apex; right paramere (Fig. 11) long, curved, narrowing upwards and divided in two opposite processes reaching both apophysis of tegmen; left paramere flat, long, divided apically and covering the base of dorsal surface of median lobe; median lobe long and slightly curved to the right; left surface of tegmen rough.

Female (Fig. 2): slightly smaller than the male; eyes smaller and more rounded; dorsal surface of elytra (Fig. 4) without sculptural modifications; seventh abdominal ventrite (Fig. 10) narrowed apicad, distal margin almost straight and with a small notch at middle; coxites (Fig. 12) small and membranous, base long and slender; styles short, wider apically.

Dimensions: Total length 7.5–9.0 mm.

Remarks: Paramaronius unituberculatus sp. nov. is similar to P. kraatzi (Pic, 1938) and P. freyi Wittmer, 1963 in the typical elytral sculpture and in the rugosity on the left surface of the tegmen. It differs from these species by the colouration of head, antennae, pronotum and legs, apex of elytra with just one tubercle (two tubercles in P. kraatzi and three in P. freyi), shape of seventh abdominal ventrite of males and females, shape of aedeagus and parameres, and less roughness of tegmen. Males of P. impressipennis (Pic, 1906), from Argentina and Brazil, differ from P. unituberculatus sp. nov. by the presence of elytra with one longitudinal ridge on posterior half, without deep grooves and tubercles. Females differ especially by the shape of distal margin of the last abdominal ventrites.