Airaphilus simulacrum Alekseev, Bukejs et McKellar sp. nov.

Alekseev, Vitalii I., Bukejs, Andris, Cooper, David M. L., King, Gavin A. & McKellar, Ryan C., 2019, A new species of Airaphilus Redtenbacher and new record of fossil Silvanidae (Coleoptera) from Eocene Baltic amber of the Sambian Peninsula, Baltic Journal of Coleopterology 19 (2), pp. 127-134 : 129-131

Airaphilus simulacrum Alekseev, Bukejs et McKellar sp. nov.

Figs. 1–2

Type material. Holotype: RSKM _ P3300.64 ; adult, sex unknown. Rather complete beetle (antennomere 11 of right antenna partially truncated) included in transparent, yellow amber piece with dimensions 19×16× 4 mm, and preserved without supplementary fixation. Syninclusions: few small detritus particles and gas vesicles.

Paratype: RSKM _ P3300.83 ; adult, sex unknown. Rather complete beetle included in small, transparent yellow amber piece embedded in block of Epo-Tek 301 resin with overall dimensions 11×5× 4 mm. Inclusion was partially damaged during epoxy embedding under vacuum: crack connecting inclusion to surface of amber piece allowed epoxy to enter body cavity and obscure many surface details originally visible in external mould within surrounding amber. Syninclusions: few small detritus particles .

Type strata. Baltic amber from Eocene amber-bearing Blue Earth layers (mostly Bartonian age, as interpreted for extinct Central European resinproducing forests according to Bukejs et al. 2019). Type locality. Yantarny settlement (formerly Palmnicken), Sambian (Samland) Peninsula, Kaliningrad region, Russia .

Etymology. Specific epithet is Latin word simulacrum , used as noun in apposition and meaning “image, likeness, phantom, shadow of dead”.

Diagnosis. Airaphilus simulacrum sp. nov. distinctly differs from other currently known Baltic amber Silvanid flat bark beetles in following characters: dorsal side of head without longitudinal grooves or striae; antennae non-filiform, gradually thickened towards apex with antennal club indistinct; lateral margin of prothorax with more than six, small, regular denticles bearing long, posteriorly directed setae; and tarsomere 3 strongly lobed.

New fossil species can be reliably differentiated from extant species of Airaphilus based on following combination of characters: exposed part of head strongly transverse, pronotum distinctly transverse, lateral pronotal margin with 12 equally-formed denticles, antennal club indistinct, humeral denticle absent, femoral lines on ventrite 1 closed, and body size comparatively large (4.0– 4.5 mm).

Description. Body length about 4.0 mm, maximum width 1.4 mm; head length 0.4 mm, head width (including eyes) 0.9 mm; pronotal length 0.9 mm, pronotal maximum width 1.1 mm; elytral length 2.8 mm, elytral maximum width 1.5 mm. Habitus elongate-oval, subparallel-sided, flattened and distinctly pubescent dorsally, slightly convex and with less conspicuous pubescence ventrally; unicolorous dark brown.

Head strongly transverse, about 2 × as wide as long, with weak constriction behind eyes; densely covered with small punctures, distance between punctures smaller than diameter of one puncture; with sparse, short, semierect setae (that are more conspicuous than setation on pronotal disc). Anterior margin of clypeus slightly and widely rounded. Fronto-clypeal suture abtinctly dilated apically; antennomere 11 ovoid, 1.5 × as long as wide.

Pronotum slightly transverse, 1.2× as wide as long, widest in anterior one-third of its length, distinctly narrowed posteriad and slightly narrowed anteriad; disc flat dorsally. Anterior pronotal edge almost straight; posterior edge convex, bordered; lateral edges slightly convex, with 12 small, sharp, regular denticles; anterior denticle not differentiated and not larger than other denticles. Anterior angles nearly rectangular, not produced anteriorly; posterior angles obtuse. Pronotal punctation large and dense, each puncture distinctly larger than compound eye facet; punctures at sides coarser than on pronotal disc; distance between punctures sent. Forehead almost flat, without grooves or striae between eyes. Temples absent. Compound eyes large, hemispherical, prominent, with coarse facets; eyes widely separated, with distance between eyes about 3 × transverse diameter of one eye. Antennal grooves absent. Antennal insertions hidden under lateral projections of frons. Maxillary palpi short; terminal palpomere elongate, spindle-shaped, about 1.8 × as long as penultimate palpomere. Antenna moderately long, extending to anterior one-fifth of elytra; 11-segmented, with indistinct club gradually thickening towards apex; sparsely covered with fine, semierect setae; scape subcylindrical, about 1.6 × as long as wide; pedicel elongate, 1.5 × as long as wide, and about 0.7 × as long as scape; antennomeres 3–6 elongate, subequal in length and shape; antennomeres 7–8 slightly elongate, about 1.2 × as long as wide, slightly dilated apically; antennomeres 9–10 as wide as long, dissmaller than diameter of one puncture, interspaces slightly convex. Dorsal pubescence fine, short, semierect, and more conspicuous laterally; each pronotal lateral denticle with one posteriorly directed, moderately long, stout, and erect seta.

Scutellar shield large, suboval, distinctly transverse, 1.4× as wide as long, with dense, small punctation, and with sparse, short, semierect setae. Elytra elongate, 1.7× as long as wide, subparallel-sided, and striate-punctate; slightly wider than pronotum; without distinct carinae. Elytral punctation dense and small (smaller than pronotal punctures); striae distinct almost throughout entire length of elytra, smoothed in apical one-third; distance between punctures in striae about 0.5–1.5× diameter of one strial puncture; interstriae almost flat (only weakly convex at base), shiny, with fine secondary punctation, distance between striae about 1.5–2.0× diameter of one puncture. Scutellary striole apparently present. Elytral pubescence composed of fine, short, semierect setae; setation more conspicuous along lateral surfaces. Humeri rounded, not protruding; humeral denticle absent. Epipleura well developed, widest at humeri, gradually narrowing posteriorly, apparently reaching elytral apex; sparsely covered with fine punctures.

Prohypomera with few, fine punctures, and strong microreticulation; prothorax with sparse, fine punctation (distinctly sparser than punctures on metaventrite). Prosternal process narrow, narrower than diameter of procoxa. Procoxal cavities apparently widely closed. Mesoventrite densely covered with large punctures, distance between punctures smaller than diameter of one puncture, interspaces slightly convex. Metaventrite impressed medially; with moderately dense cover of fine punctation, distance between punctures distinctly larger than diameter of one puncture, interspaces microreticulate; pubescence composed of fine, sparse, recumbent setae. Metepisterna long and narrow, slightly widened anteriorly; inner lateral margin almost straight, outer lateral margin slightly concave; sparsely covered with fine punctation and fine, recumbent pubescence.

Legs moderately short and robust; sparsely covered with fine, recumbent setae. Procoxa nearly round, mesocoxa widely oval, metacoxa transverse, oval; all coxae separated from each other. Trochanters without spines. Femora widened medially, simple (without teeth), with deep, longitudinal groove apicoventrally; metafemora more widened medially than pro- and mesofemora. Tibiae almost straight, not dilated apically, nearly as long as femora; without denticles or spines; with fringe of spinules apically. Tarsi pentamerous, long; tarsomeres 2–3 slightly dilated apically, tarsomere 3 ventrally produced in front to form lobe; tarsomere 4 very small; tarsomere 5 longest, nearly as long as tarsomeres 1–3 combined. Tarsal claws simple, apparently slightly widened basally, equal in size, long, about 0.35× as long as apical tarsomere.

Abdomen with five visible, similarly articulated ventrites; ventrite 1 with closed postcoxal line (forming margin of metacoxal cavities); densely covered with fine punctation, distance between punctures about 0.7–2.0× diameter of one puncture, interspaces microreticulate; abdominal pubescence moderately dense, composed of fine, short, recumbent setae; sutures straight; ventrite 5 rounded apically. Intercoxal process of abdominal ventrite 1 triangular, narrow, and acute. Relative length ratio (medially) of ventrites 1–5 equal to 18:12:10:8:5.

Paratype. Body length about 4.5 mm, maximum width 1.8 mm; head length (?) 0.5 mm, head width (including eyes) 1.1 mm; pronotal length 1.0 mm, pronotal maximum width 1.3 mm; elytral length 3.0 mm, elytral maximum width 1.8 mm. Relative length ratio of antennomeres 1–11 equal to 13:10:10:11:10:10:10:10:10:9:11.

Figures

Fig. 1. Airaphilus simulacrum sp. nov., holotype, RSKM_P3300.64:A – dorsal habitus; B – ventrolateral habitus. Scale bars represent 1.0 mm.

Fig. 2. Airaphilus simulacrum sp. nov., paratype, RSKM_P3300.83:A – dorsal habitus; B – ventral habitus; C – condition of specimen before epoxy infilling obscured surface details, dorsal habitus. Scale bars represent 1.0 mm.