Protonaupactus sobrinus (Voss, 1972) Voss, 1972

Yunakov, Nikolai N. & Kirejtshuk, Alexander G., 2011, New genus and species of broad-nosed weevils from Baltic amber and notes on fossils of the subfamily Entiminae (Coleoptera, Curculionidae), ZooKeys 160, pp. 73-96 : 81-85

Protonaupactus sobrinus (Voss, 1972) comb. n. Figs 19-34

Phyllobius sobrinus Voss 1972: 174

Sucinophyllobius sobrinus Wanat & Borowiec 1986: 243

Material examined.

Holotype: ZMUC903847, male (ZMUC); the complete beetle is included in a nearly regular amber piece, parallelepiped, with facets 14.0, 10.0 and 5.0 mm; one thin layer with wavy, light organic matter, small gas bubbles and small cracks located beneath the beetle.

Type strata.

Baltic Amber; Upper Eocene, Prussian Formation.

Type locality.

Denmark "Bernschteinschluss, Versterhavet bei Thisted, 17.xii.1895, Madsen leg.".

Redescription.

Length 4.5, width 1.75, and height 1.65 mm. Beetle densely covered with metallic, shining scales (apparently green).

Head. Rostrum 1.5 times as long as wide at level of pterygia. Epifrons subparallel-sided, at level of antennal insertions abruptly widened anteriorly, weakly convex longitudinally, separated from frons by a distinct depression indicating a transverse sulcus hidden by dense scales. Pterygia strongly extending beyond lateral contour of rostrum. Epistome well-defined by U-shaped keel. Epistomal setae grouped in dense bunches at anterior epistomal angles. Each bunch bearing at least 5 setae. Epistomal angles pronounced apically. Anterior edge of pterygia densely setose. Antennal furrows distinct only in their basal half and not continuing obliquely to underside of rostrum, their dorsal and ventral edges somewhat divergent posteriorly. Eyes dorso-lateral, round and evenly convex. Frons slightly convex, as wide as epifrons between antennal insertions. Frontal fossa not visible because masking by scales. Antennae long. Scape straight, evenly thickened apically, reaching anterior constriction of pronotum. Funicle thin: pedicel about 0.7 time as long as 2nd funicular article; 2nd article about 3.5 times as long as wide; 3rd -7th articles weakly oblong, about 1.5 times as long as wide. Club ovoid, about 2.3 times as long as wide, its 1st article significantly different in shape from 7th funicular article.

Pronotum transverse; evenly convex at sides and disc, strongly constricted anteriorly and posteriorly. Its base slightly bisinuate. Anterior edge of pronotum straight, without postocular lobes, spurs or vibrissae. Scutellum significantly pronounced, subquadrate.

Elytra subparallel, hardly widened in apical half, with pronounced humeral prominences. Epipleural edge weekly but distinctly S-shaped. Wings well-developed, beetle apparently capable of flying. Elytral declivity abruptly sloping. Anterior edge of anal ventrite (hypopygidium) emarginate (Fig. 30).

Legs thin. Femora obtuse, weakly swollen in middle part. Protibiae straight at external edge, not widened at external apical angle. Metatibiae spatulate apically (Fig. 33), with open corbel but without additional setal row. Setal comb of all tibiae weakly-developed. Tarsi with well-developed setaceous pelma (term after Doyen 1966). Tarsomere 1 about as long as tarsomeres 2 and 3 combined. Tarsomere 3 with well-developed lobes. Ultimate tarsomere by 0.7 extending beyond lobes of tarsomere 3. Claws free.

Differential diagnosis.

This species is distinguished from Protonaupactus microphthalmus and Protonaupactus viridis by the metatibiae being strongly spatulate apically. The re-examination of the holotype of Phyllobius sobrinus Voss, 1972 demonstrates the particular structure of the head, which is very similar to some genera of Anypotactini (mostly from tropical America) and Cyphicerini (mostly from Old World tropics, distinctly separated groups): epistome U-shaped, convex, weakly sinuate anteriorly, and claws free (Figs 27, 31). This species also shares a well-developed, transverse sulcus on the rostrum (Fig. 25, 26, 35-39) with other groups of Anypotactini .

Notes on synonymy.

The comparison of Sucinophyllobius sobrinus , Sucinophyllobius viridis and Protonaupactus microphthalmus shows they are closely related species of the same genus. They share almost the same characters of the rostrum, with moderately defined U-shaped epistome having apically pronounced angles, long and slender antennae with the scape extending behind the anterior margin of the pronotum, funicular article 1 about 0.7 × as long as article 2, and article 2 about 3.5 × as long as wide.

Systematic position of Protonaupactus

Anypotactini and Cyphicerini are the only tribes of Entiminae whose relationships with Protonaupactus still need to be tested. Both tribes contain genera with the following characters: (1) claws free, (2) epistome deeply sinuate, parepistome distinctly protruding and bearing dense bunches of long setae, (3) swinging fossae long, fully visible in dorsal view, (4) pterygia strongly extended beyond rostrum.

The tribe Cyphicerini consists of rather diverse genera which may be divided into two subgroups by the structure of the prothorax and underside of the head: (1) a prosternum subflattened with straight anterior edge; b pronotum with straight anterior edge; c rostrum and head united in a consolidated structure; d underside of rostrum densely covered with scales, its sculpture uniform; e rostrum directed forwards ( Mylacorrhinina and Myllocerina ) or (2) a prosternum with anterior edge sinuate; b pronotum with distinct postocular lobes; c head and rostrum distinctly separated by transverse constriction; d basal area of underside of rostrum with glabrous integument which has a bare stripe reaching the eyes; e rostrum directed downwards ( Acanthotrachelina , Cyphicerina , and Phytoscaphina ).

Anypotactini include a group of genera that share a character set characteristic of the subgroup I of Cyphicerini and distinct from this subgroup in the transverse sulcus on the rostrum. However, this tribe displays an enormous variety in rostrum shape, and also shows both dorsal and lateral positions of the antennal scape which is normally folded above the eyes, along the rostrum, or folded obliquely downwards in the scrobe if developed. Both the antennal scape and funicle are quite slender, hence the antennae resemble a brachyderoid rather than otiorhynchoid type, like in Cyphicerini .

Anypotactus Schoenherr 1840, Polydacrys Schoenherr, 1833 and other genera with short rostrum and large pterygia belong to Anypotactini subgroup 1, and Prepodellus Kirsch, 1867, Hyphantus Germar, 1824 and other genera with long rostrum with very small pterygia belong to Anypotactini subgroup 2.

Protonaupactus combines both character sets, Anypotactini and Cyphicerini . Nevertheless, it can be easily distinguished from Cyphicerini subgr. 2 in sharing the basic character set of Cyphicerini subgr. 1 and Anypotactini subgr. 1. From Cyphicerini subgr.1 Protonaupactus differs particularly in the transverse sulcus on the rostrum (Fig. 25, 26). The new data on this fossil genus show that the distinctness between these tribes is not very clear and needs a further investigation.