Pseudomesauletes lobanovi, Bukejs & Legalov, 2021

Bukejs, Andris & Legalov, Andrei A., 2021, Two new species of the family Rhynchitidae (Coleoptera: Curculionoidea) from Eocene Baltic amber, with key to species and assumed trophic relationships, Fossil Record 24 (1), pp. 117-127 : 122-124

Pseudomesauletes (Pseudomesauletes)

lobanovi sp. nov.

urn:lsid:zoobank.org:act:98039B3C-9475-479D-AF44-

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Fig. 3 .

Etymology

Patronymic. The name of this new species is dedicated to the memory of the late Andrey L’vovich Lobanov, known specialist in Cerambycidae and founder of coleopteran website “Beetles and Coleopterists” (http://www.zin.ru/animalia/ coleoptera/eng, last access: 30 April 2021).

Type material

Holotype: collection number “6701” ( MAIG) (ex. coll. Jonas Damzen JDC 9318), “ Holotype / Pseudomesauletes / lobanovi sp. nov. /Bukejs et Legalov des. 2021” (red printed label); adult, female. A complete beetle included in a transparent, yellow amber piece with approximate dimensions of 33 mm × 11 mm and a maximum thickness of 7 mm; preserved without supplementary fixation. Syninclusions: one Diptera specimen, body parts (legs and wing) of cf. Diptera, few stellate trichomes, and some small gas vesicles.

Type stratum

A predominantly Bartonian age (41.3–37.9 Ma) is interpreted for the extinct central European resin-producing forests, which produced the amber that has eroded out of Eocene Blue Earth layers (Bukejs et al., 2019). However, the vast majority of Baltic amber derives from the geological amber-bearing strata of the certainly Priabonian age (37.8– 33.9 Ma) ( Sadowski et al., 2017, 2020).

Type locality

Baltic Sea coast, Yantarny settlement (formerly Palmnicken), Sambia (Samland) Peninsula, the Kaliningrad Region, Russia.

Description

Measurements. Body length (without rostrum) about 3.3 mm, body maximum width 1.4 mm; rostrum length 1.9 mm, rostrum width basally 0.3 mm, medially 0.2 mm, apically 0.3 mm; pronotum length 1.0 mm, pronotum maximum width 0.9 mm; elytra length 2.2 mm, elytra maximum width 1.4 mm.

Body. Brown (as preserved), head and rostrum dark brown. Pubescence: rather dense, short and recumbent.

Head. Dorsally covered with small, sparse punctation, distance between punctures about 0.5–1.5 × diameter of one puncture, ventrally with sharp transverse wrinkles and very sparse punctation; forehead wide, convex; vertex slightly impressed. Rostrum very long, about 1.9× as long as pronotal length, almost straight (in lateral view), widened to apex (in dorsal view), about 6× as long as wide basally, 9.5× as long as wide medially, and 6× as long as wide apically; sparsely covered with fine punctures, punctation denser in basal portion; with longitudinal carina in basal one-third of rostral length. Rostral pleurostomal sinus deep and membranous. Mandibles externally dentated. Maxillary palpi four-articled. Gular suture single. Compound eyes rather large, subspherical, strongly convex.

Antennae. With 11 antennomeres, not geniculate, with distinct three-antennomered club; moderately long, about 0.7× as long as rostrum length, reaching anterior one-third of pronotum, inserted in basal one-third of rostral length, sparsely covered with semierect setae; scape cylindrical, 2× as long as wide, 0.6× as long as antennomere 2, antennomeres 2–6 elongate-oval, antennomere 3 about 1.3× as long as antennomere 2, antennomeres 7–8 short, slightly dilated apically, antennal club about as long as antennomeres 5–6 combined, antennomere 9 as long as wide, dilated apically, wide, about 2× as wide as antennomere 8; antennomere 10 slightly transverse, dilated apically, wide, antennomere 11 elongate oval with tapered apex; relative length ratios of antennomeres 1–11 equal to 7: 11: 14: 11: 9: 6: 5: 3: 5: 5: 7.

Pronotum. Nearly as long as wide, widest medially, narrowed posteriad and anteriad; densely covered with small punctation (punctures distinctly larger than punctures of head), distance between punctures about 0.3–1.1× diameter of one puncture (punctation on disc sparser); disc evenly convex; lateral margins convex medially and subparallel anteriorly and posteriorly, posterior margin straight, anterior margin convex in dorsal view.

Scutellum . Subpentagonal with widely rounded apex, transverse, about 1.25× as wide as long, rather large, densely covered with fine punctation.

Elytra. Almost rectangular, elongated, widest behind middle, convex, not ribbed, in anterior one-third slightly impressed medially; elytral base distinctly wider than posterior pronotal margin; humeral callus weak; elytral punctation small and dense, forming regular rows (distinct in basal half), intervals flat; elytral apices rounded together, without large depressed spots and hair stains.

Thorax. Prohypomera with small, dense punctation (as pronotal punctation). Epipleuron narrow. Metaventrite and metepisternum with fine and very dense punctation.

Legs. Long, slender. Femora spindle-shaped, slightly flattened, covered with fine, sparse punctation. Tibiae cylindrical, almost straight, slightly dilated distally, with fringe of dark spinula apically, lacking costate dorsal margin. Tarsi distinctly shorter than tibiae, protarsus about 0.5× as long as protibial length; tarsomere 1 trapezoidal, elongate, not extended, tarsomere 2 trapezoidal, distinctly dilated apically, tarsomere 3 wide, deeply bilobed, with dense setation ventrally, terminal tarsomere elongated, subcylindrical, slightly curved. Tarsal claws slightly divergent, free, with long spine basally.

Abdomen. Convex, covered with small punctation; ventrites almost homonomous; ventrites 1–3 fused; ventrite 2 1.4× as long as ventrite 1; ventrite 3 subequal to ventrite 2 and 2.1× as long as ventrite 4; ventrite 4 about 1.7× as long as ventrite 5; ventrite 5 smallest, with rounded apical margin.

Note

The specimen is a female: elytral apex lacks hair stains, and abdominal ventrites 1–3 are fussed.

Comparison

Pseudomesauletes lobanovi sp. nov. is similar to the North American Eocene species P. culex ( Scudder, 1893) and P. ibis ( Wickham, 1912) , in the long rostrum, almost equal to the length of the elytra. The new species differs from P. culex in the large eyes; longer pronotum, 0.44× shorter than elytra (0.25× shorter than elytra in P. culex ); and slightly smaller body size. It differs from P. ibis in the small body size, rostrum shorter than elytra, and weakly convex pronotum. Additionally, the new species differs from P. groehni Bukejs et Legalov, 2019 from Rovno amber in the long rostrum and narrower antennae club.

Key to the Eocene species of the genus Pseudomesauletes

1. Rostrum 1.4 times as long as elytra. Body large, 7.0 mm. Florissant ( ibis ( Wickham, 1912)) .

– Rostrum shorter than elytra. Body less than 6.1 mm (p. 2).

2. Rostrum longer, 0.92–0.96× shorter than elytra (p. 3).

– Rostrum shorter, 0.58–0.85× shorter than elytra (p. 4).

3. Eyes large. Pronotum 0.44× as long as elytra. Body length 3.3 mm. Baltic amber ( lobanovi sp. nov.).

– Eyes small. Pronotum 0.25× as long as elytra. Body length 4.2 mm. Florissant ( culex ( Scudder, 1893)) .

4. Rostrum longer, 0.85× shorter than elytra. Body large (6.1 mm). Florissant ( obliquus ( Wickham, 1913)) .

– Rostrum shorter, 0.57–0.58× shorter than elytra. Body smaller, 3.2–4.9 mm (p. 5).

5. Body larger, 4.9 mm. Rostrum 4.0× as long as wide apically. Florissant (striaticeps ( Wickham, 1911)).

– Body smaller, 3.2 mm. Rostrum 6.25× as long as wide apically. Rovno amber ( groehni Bukejs et Legalov, 2019 ).

Remarks

The studied amber specimen belongs to the family Rhynchitidae based on the not geniculate antennae, single gular suture, narrow epipleuron, four-articled maxillary palpi, ventrites 2 and 3 subequal in length, not extended tarsomere 1, tarsal claws free at base, and deep and membranous rostral pleurostomal sinus. Slightly divergent tarsal claws suggest its placement in the subfamily Rhynchitinae and externally dentated mandibles – in the supertribe Rhynchititae . Rounded apex of the elytra when both together confirm the assignment of the species to the tribe Auletini . The new species belongs to the subtribe Pseudomesauletina based on the tarsal claws with a spine, tibia lacking costate dorsal margin and antennae being inserted before middle of the rostrum. The body is covered with short sparse recumbent setae, elytra are not ribbed, elytral apices are without large depressed spots, antennomere 3 is longer than antennomere 2, antennae are inserted before the middle of the rostrum, and eyes are strongly convex, which suggest placement in the genus Pseudomesauletes . The specimen was assigned to the subgenus Pseudomesauletes s. str. on the basis of the almost rectangular elytra and the brown body colouration.

Figures

Figure 3. Photomicrographs of Pseudomesauletes lobanovi sp. nov., holotype, 6701 (MAIG), habitus: (a) dorsal view; (b) ventro-lateral view; (c) right lateral view. Scale bars = 1.0 mm.