Mucronotus enigmaticus, Ruta, 2021

Ruta, Rafał, 2021, Three new genera of large marsh beetles (Coleoptera: Scirtidae) from Valdivian temperate rain forests of southern South America, Zootaxa 5048 (4), pp. 451-485 : 466-468

Mucronotus enigmaticus sp. nov.

( Figs 10A–B , 13A–B , 14–15 )

Type material. Holotype, male ( FMNH): “ CHILE: Arauco: Alto \ Llupehue , 4.I.1977 \ L. E. Pena leg. \ FIELD MUS. NAT. HIST.” . Paratypes, 1 male, 2 females ( FMNH): same data as holotype . 1 male ( CMNC): “ CHILE: Malleco; Puren \ Contulmo Natur Mon \ 11.XII.84-13.II.85 \ S&J Peck, FIT, 350 m \ mixed evergr. forest” .

Diagnosis. Posterolateral angles of pronotum well marked; elytra covered with dense but small punctures; processes of trigonium shorter than pala, bisinuate, with ca. 30 denticles on its outer margin and distinct basal lobe; anterior portion of bursal sclerite transversely oval.

Description. Male. Body moderately large (TL 7.2–7.8 mm), elongate (TL/EW 1.8), widest in the middle of elytra, moderately convex. Colouration chestnut brown. Head ca. 1.5× wider than interocular space, convex, densely covered with strong, granulate punctation, punctures separated by 0.3–0.5× diameter of a puncture; eyes moderately large, protuberant. Pronotum transverse (PW/PL 2.14), covered with dense (separated by 0.3–0.5× diameter of a puncture), strongly granulate punctures on sides and sparse punctures on central portion, lateral carinae of pronotum rounded, posterolateral angles well marked, anterolateral angles subtriangular. Elytra long, 4.4× longer than pronotum, 1.4× wider than pronotum; punctation irregular, sparse, separated by ca. the diameter of a puncture. Aedeagus symmetrical, penis ( Fig. 14B ) large (L 1.32 mm, W 0.64 mm), dorsoventrally flattened; trigonium bifid, each process of trigonium sinuate, with curved lobe at base, outer margin with ca. 30 denticles; parameroids subtriangular, narrowed in apical portion, apices reaching apices of trigonium. Tegmen ( Fig. 14C ) large (L 1.48 mm, W 1.14 mm), subrectangular, on each side with small, subtriangular lateral process; ventral processes wide, each with two lobes (subtriangular and suboval one); parameres digitiform, densely covered with short setae. Sternite VIII ( Fig. 14D ) (L 0.64 mm, W 1.04 mm) widely v-shaped, with sparse setation at apex; sternite IX ( Fig. 14E ) (L 0.74 mm, W 1.02 mm) oval, consisting of two subtriangular hemisternites, apical portion covered with setae. Tergite VIII ( Fig. 14F ) large (L 1.1 mm, W 1.06 mm), apodemes shorter than apical plate, apical plate subtrapezoidal, covered with microsetae, apical margin rounded, with a row of sparse setae. Tergite IX ( Fig. 14G ) (L 1.06 mm, W 0.74 mm) with short apodemes, apical portion membranous, setation indistinct.

Female. Body slightly smaller (TL 6.5–7.5 mm), setation of dorsum dense, recumbent; head with coarse punctures separated by ca. 0.3× diameter of a puncture; disc of pronotum more convex than in males; pronotal disc densely covered with small, not granulate punctures, lateral sides of pronotum with coarse, confluent, granulate punctures; punctures on elytra separated by ca. 0.5–1.0× diameter of a puncture; ovipositor long (L 3.9 mm, Fig. 15A ), without branchlets, coxites subtriangular, elongated, apices of coxites with numerous short setae, styli apical, with two single patches of sensillae, bursal sclerite (L 1.6 mm, W 0.84 mm) elongate, with transversely oval sclerotization in anterior portion ( Fig. 15B ).

Measurements and ratios. Males (n = 3) TL 6.20–7.80 mm (7.1 mm), PL 1.20–1.50 mm (1.3 mm), PW 2.50–3.20 mm (2.8 mm), EL 5.10–6.40 mm (5.8 mm), EW 3.25–4.20 mm (3.9 mm), TL/EW 1.7–1.9 (1.8), PW/PL 2.1–2.2 (2.1), EL/EW 1.4–1.6 (1.5), EL/PL 4.3–4.5 (4.3), EW/PW 1.3–1.5 (1.4). Females (n = 2) TL 6.50–7.50 mm (7.00 mm), PL 1.20–1.30 mm (1.25 mm), PW 2.70–3.10 mm (2.90 mm), EL 5.20–6.30 mm (5.75 mm), EW 3.50– 4.10 mm (3.80 mm), TL/EW 1.8–1.9 (1.8), PW/PL 2.3–2.4 (2.3), EL/EW 1.5 (1.5), EL/PL 4.3–4.9 (4.6), EW/PW 1.3 (1.3).

Distribution. A very rare species, known from two localities in the northern part of the Araucanía region of Chile ( Fig. 24A , see Remarks below).

Biology. The species was collected in Valdivian temperate forest.

Etymology. Greek αινιγματικός—mystery, riddle, a reference to the uncertain locality of the species (see Remarks below) and its extreme rarity.

Remarks. Locality of specimens from the collection of FMNH is probably misspelled and refer to the environs of Yupehue in Cautin province of Araucanía region (approximate coordinates: 38°32’57.72”S, 73°26’17.77”W).

Figures

FIGURE 10. Mucronotus gen. nov., dorsal view. A) M. enigmaticus sp. nov., male; B) M. enigmaticus, female; C) M. pat- agonicus sp. nov., male; D) M. schwabei (Pic), male; E) M. schwabei (Pic), female; F) M. valdivianus sp. nov., male; G) M. valdivianus sp. nov., female; H) M. velutina (Solier), male; I) M. velutina (Solier), female. Scale bar = 2.0 mm

FIGURE 13. Mucronotus gen. nov., pronotum. A) M. enigmaticus sp. nov., male; B) M. enigmaticus sp. nov., female; C) M. patagonicus sp. nov., male, D) M. schwabei (Pic), male, E) M. valdivianus sp. nov., male, F) M. velutinus (Solier), male.

FIGURE 14. Mucronotus enigmaticus sp. nov., male.A) terminal segments and genitalia; B) penis; C) tegmen; D) sternite VIII; E) sternite IX; F) tergite VIII; G) tergite IX. Abbreviations: bl—basal lobe (of trigonium), lp—lateral process, pm—paramere, pmd—parameroid, tgp—process of trigonium, vpl—ventral processes of tegmen. Scale bar = 0.5 mm.

FIGURE 15. Mucronotus enigmaticus sp. nov., female.A) genital tract; B) bursal sclerite.Abbreviations: bscl—bursal sclerite, bsl—bursella, gla—gland. Scale bars = 1.0 mm (A), 0.5 mm (B).

FIGURE 24. Distribution of Mucronotus gen. nov. A) M. enigmaticus sp. nov. (blue dots) and M. patagonicus sp. nov. (red dots); B) M. schwabei (Pic); C) M. valdivianus sp. nov.; D) M. velutinus (Solier).