Baltacalles triumurbium, Bukejs & Alekseev & Legalov, 2020

Bukejs, Andris, Alekseev, Vitalii I. & Legalov, Andrei A., 2020, A new Eocene genus of the subtribe Tylodina (Coleoptera: Curculionidae) and notes concerning local differences of Baltic amber in the Kaliningrad Region, Fossil Record 23 (1), pp. 75-81 : 76-78

Baltacalles triumurbium sp. nov. urn:lsid:zoobank.org:act:064999A3-EE1E-4A7B-9E5F-2F77BE3FB31C ; Figs. 1–2

Etymology

Specific epithet is formed after the Latin phrase tres urbs in the genitive case and is the toponym referring to Trójmiasto (“Tricity”) – a metropolitan area consisting of three cities (Gdańsk, Sopot and Gdynia) on the coast of the Gdańsk Bay.

Type material

Holotype: 6274 (ex. coll. Jonas Damzen JDC 8115) ( MAIG); adult, sex unknown. Complete beetle is included in elongate, transparent amber piece, with dimensions of 34 × 9 × 7 mm. Syninclusions: one specimen of Nematocera (Diptera), few stellate Fagaceae trichomes, and many small gas vesicles.

Type stratum

Baltic amber from Eocene amber-bearing Blue Earth layers, mostly Bartonian age is interpreted for the extinct central European resin-producing forests according to Bukejs et al. (2019).

Type locality

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

Description

Measurements: body length (without rostrum) 5.2 mm, body maximum width about 2.8 mm, rostrum length about 1.7 mm; pronotum length 1.3 mm, pronotum maximum width 1.85 mm; elytra length 3.8 mm, elytra maximum width about 2.8 mm.

Body elongated oval, moderately convex; integument unicolorous, dark brown (as preserved).

Pubescence: dorsum moderately densely covered with short, elongate, almost recumbent brown scales; elytra additionally with two moderately long, erect setae latero-apically; anterolateral parts of prosternum additionally with long, curved seta; head (anteriorly) and rostrum (basally) with sparse, short, stout setae, rostrum with few long, erect setae apically; venter and legs moderately densely covered with short, stout setae, abdominal ventrites 3–5 with slightly denser and finer setation.

Head densely covered with small punctation, distance between punctures less than the diameter of one puncture, interspaces slightly convex, with secondary micropunctation. Rostrum long, 1.3× as long as pronotum, about 4.3× as long as wide at apex, 2.9× as long as wide at base and medially; distinctly narrower than head capsule; with fine, sparse punctation and microreticulation, and apparently with shiny, glabrous longitudinal area dorsally; antennal scrobes lateroventral. Forehead narrow, almost flat. Vertex slightly convex. Compound eyes large, hemispherical, convex, with large facets; partially covered by anterolateral sides of prosternum. Antennae geniculate, with 11 antennomeres, clavate, moderately long, sparsely covered with fine setae, with distinct 3- segmented club; scape long, about as long as antennomeres 2–3 combined, slightly dilated apically; antennomeres 2–3 equal in size and shape, strongly elongate, about 4.3× as long as wide; antennomeres 4–6 slightly elongate, subcylindrical; antennomeres 7–8 distinctly dilated apically, about as wide as long; antennal club compact, spindle-shaped, rather short; antennomeres 9–10 transverse, 1.2× as wide as long; antennomere 11 conical with pointed apex, about 0.8× as wide as long; relative length ratios of antennomeres 1–11 equal to ∼ 32-17-17-9-9-6-6-6-8-8-11.

Pronotum nearly bell-shaped, widest in basal one-third, transverse, 1.4× as wide as long, narrower than anterior elytral margin, with weak constriction at anterior margin, distinctly narrowed anteriad and slightly narrowed posteriad, disk slightly convex; densely covered with large punctation, distance between punctures less than the diameter of one puncture, some discal punctures almost contiguous, interspaces slightly convex, with secondary micropunctation; lateral margins evenly slightly convex, anterior margin slightly convex, posterior margin almost straight.

Scutellum minute, distinct, roundish, apparently impunctate.

Elytra elongate, about 1.4× as long as maximum wide, 2.9× as long as pronotum, subparallel-sided, punctatestriate, humeral calli weakly convex, basal margin slightly concave. Elytral punctures small and dense (discal punctation larger and denser), arranged in regular rows, distance between punctures in rows equal to 0.7–1.5× diameter of puncture; intervals distinctly convex, distance between rows about 2–2.5× diameter of puncture; sutural stria lacking.

Prohypomera convex in anterior portion, densely covered with moderately large punctures, distance between punctures smaller than diameter of one puncture, interspaces convex. Anterolateral parts of prosternum convex, projecting anteriad. Metepisternum narrow, with moderately small and sparse punctures. Metaventrite with large, dense punctures, interspaces convex; slightly narrower (medially) than abdominal ventrite 3.

Abdomen: with five visible ventrites oriented in one plane; abdominal punctation fine to small: ventrites 1–2 with small, sparse punctures laterally and with fine, sparse punctures medially, ventrites 3–4 with fine, moderately dense punctures, ventrite 5 with fine and denser punctures; abdominal suture between ventrites 1–2 fine, visible laterally only, obsolete medially, abdominal sutures between ventrites 2–5 distinct throughout its length, sharp and deep; intercoxal process of ventrite 1 wide, apparently slightly wider than transverse diameter of metacoxa; ventrites 1–2 with shallow impression medially; ventrite 5 with widely rounded apex; relative length ratios of abdominal ventrites 1–5 equal to 24-16-7-7- 16 (medially).

Legs long, slender, densely covered with small punctures. Procoxae subconical, located in posterior portion of prothorax; mesocoxae hemispherical, separated by nearly 1× diameter of mesocoxa; metacoxae widely oval, transverse, about 2.3× as wide as long, widely separated by about 1× transverse diameter of metacoxa. Femora elongate, clavate, swollen in apical portion, with ventral denticle, slightly longer than femora. Tibiae moderately robust, slightly flattened, slightly curved inwards, with large uncus, and two groups of setae; protibiae distally without mouth groove and row of dense erect setae (grooming device); mesotibiae without denticle in middle of exterior margin. Tarsi moderately long (protarsus 0.6× as long as protibia), setaceous, pelma well-developed; tarsomere 1 elongate, dilated apically, 1.5– 1.6× as long as tarsomeres 2, tarsomere 2 transverse, trapezoidal, tarsomere 3 deeply bilobed, transverse, ultimate tarsomere elongate, projecting from tarsomere 3 to about half of its length. Tarsal claws small, free, simple.

Figures

Figure 1. Baltacalles triumurbium gen. et sp. nov., holotype, 6274 (MAIG): (a) habitus, dorsal view; (b) habitus, ventrolateral view; (c) habitus, left lateral view. Scale bars = 1 mm.

Figure 2. Baltacalles triumurbium gen. et sp. nov., holotype, 6274 (MAIG): (a) forebody, lateral view; (b) details of left elytron, dorsal view. The arrows indicate long setae. Scale bars = 0.5 mm.