Holotype ♂ (MECN-EN 23780): “Ecuador. Napo: Chontapunta, R. Minga, -0.88692, -77.27049, 300 m. Winkler. 07-feb-2023, Díaz-Guevara & N. Berrazueta” / “MECN-EN 23780”; deposited in MECN.

Ecuador • 1 ♀; Orellana; 0.6376°S, 76.1499°W; Tiputini Biodiv. Sta.; 2-9.vi.2011; general hand collecting, AT1341, M. Caterino, A. Tishechkin; Caterino DNA voucher, Ext. MSC-12663; ZSFQ-i16787 • 1 ♀; Panayacu, Yasuní, 0°42'17.6"S, 76°40'15.7"W; 340 m; Winkler; 17 Jul. 2021; Pazmiño-Palomino; MECN-EN 48730.

Metopiellus palamaku sp. nov. strongly resembles M. guanano, having a vertex with a single horn-like projection. However, M. palamaku can be easily differentiated by its single pair of mediolateral, thick, spinose pronotal projections (vs. two pairs in M. guanano), the presence of basal elytral foveae (absent from M. guanano), and by aedeagal characters including a more elongate basal bulb, and differently shaped articulated armature (Fig. 2), bifid at the tip with subapical hook bent at ~90° (vs. aedeagal armature simply tapered, slightly sinuate at apex in M. guanano; aedeagal armature with four spatulate, curved tips in M. emavieirae).

Avg. BL = 2.7 mm (N = 2; see Table 1 for other measurements). Body (Fig. 1A–C) densely setose and brown; eyes prominent, comprising ~11 ommatidia; head pyriform with two vertexal foveae near posterior margin with a single median process similar to M. guanano; antennae with 11 antennomeres, antennal scape base thick and slightly narrowed before the apex (in dorsal view), antennomere I as long as rest of the antennomeres combined, antennomere II about as long as III–VIII combined, III-IV and VI slightly longer than wide, V distinctly longer, VII globular, VIII small, IX and X slightly transverse, XI almost as long as IX–X combined, tapered in apical half; pronotum trapezoidal, wider anteriorly and narrower posteriorly, with two pairs of mediolateral, thick, spinose projections; each elytron with two basal foveae, and with longitudinal impressions extending from them posteriorly approximately two-thirds elytron length. Aedeagus (Fig. 2A–C) with large, elongate basal bulb, slightly asymmetrical, with smoothly rounded basal margin; dorsal diaphragm large, elongate oval; tegmen narrowed toward flat, paddle-shaped apex; elongate armature articulated within basal bulb, apex bifid, with acute, subapical hook bent at ~90°, other tip slightly diverging to left, acute.

This species is known from the type locality in Chontapunta, Ecuador (Fig. 3), and probably also from the Tiputini region of Orellana (if the associations of the females under ‘other material’ are correct). The sites are separated by about 125 km, but are all on the same (south) side of the Rio Napo.

The specific name derives from a Kichwa legend in which Palamaku is the divine source of insects.

Holotype ♂ (QCAZ 280376): “Ecuador. Pichincha: Otongachi Reserve -0.330510, -78.934420, 1087m.20-Feb-2020, E. Tapia & N. Dupérré”; deposited in QCAZ. Paratypes (4 ♀, same general locality as type): -0.330510, -78.934420, 1087 m (QCAZ 280377 to 280380).

Ecuador • 4 ♂, 4 ♀: Zamora Chinchipe; Las Orquídeas; -4.2482, -78.6595; 877 m; E. Tapia; Sifting litter; 29-Jul-2024; QCAZ 280381 to 280388.

Metopiellus chasqui resembles M. emavieirae in the presence of a pair of (rather than a single) vertexal structures and by having two pairs of mediolateral pronotal projections. However, it can be distinguished from it by the vertexal and median pronotal processes being transversely ridge-like, and by the lateral pronotal processes having a posterior acute point (vs. horn-like vertexal and pronotal structures in M. emavieirae). The aedeagi differ strongly, with that of M. chasqui having a strongly bifurcate dorsal armature, and that of M. emavieirae being subdivided subapically into four curved, spatulate tips.

Avg. BL = 3.2 mm (N = 2; see Table 1 for other measurements). Body (Fig. 1D–F) densely setose and brown-reddish; eyes prominent, borne on small elevated base, comprising ~8 ommatidia; head widest at base, rounded, narrowed anterad, with two posterior vertexal foveae (Fig. 1E) immediately in front of two low posterior vertexal ridges; antennae with 11 antennomeres, antennal scape about as long as antennomeres II–VIII combined, antennomere II as long as III–VII combined, III–VI elongate, V longer than others, VII globular, VIII smallest, IX–XI forming weak club, IX and X transverse, XI almost as long as IX and X combined, tapered in apical two-thirds; pronotum densely setose, with 4 acute lobes, lateral lobes each with posterior acute point, median ones forming oblique ridges, prominent at their inner corners; each elytron with two basal foveae, and with longitudinal impressions extending from them posteriorly approximately two-thirds elytron length; protibia rather slender. Aedeagus (Fig. 2D–F) with basal bulb asymmetrical and globose, with basal rounded margin, elevated distad, dorsal diaphragm elongate oval; tegmen with ventral portion long, slender, curved dorsad and then distad apically; articulated armature robust, deeply bifurcated, one bifurcation is hook-like, longer and evenly tapered, other more robust with small projection oriented towards distal apex of basal bulb.

This species probably only occurs in the Otongachi Reserve in northern Ecuador, in the province of Pichincha (Fig. 3). We believe the ‘additional material’ cited from Zamora-Chinchipe to be mislabeled, since that locality is over 400 km to the south, and located on the Amazonian side of the Andean crest, an unlikely distribution for a flightless beetle species. The male genitalia is identical between the two alleged localities.

The specific epithet “chasqui” refers to the agile messengers of the Inca Empire, evoking the beetle’s slender posterior legs.