Protostomopsis pandema Bukejs, Ślipiński et Alekseev, 2021

Bukejs, Andris, Ślipiński, Adam, Mitchell, Jerit L., Mckellar, Ryan C., Bi, Mauricio Bar-, Larsson, Hans C. E. & Alekseev, Vitalii I., 2021, First fossil representative of Cerylonidae (Coleoptera: Coccinelloidea) described using X-ray micro-computed tomography, from Eocene Baltic amber, Zootaxa 5032 (2), pp. 225-236 : 227-234

Protostomopsis pandema Bukejs, Ślipiński et Alekseev sp. nov.

( Figs 1–6 )

http://zoobank.org/ urn:lsid:zoobank.org:act:57685E94-A433-4343-A133-44E2FCEEB309

Type material. Holotype: Nr. MP/4233 /col. AG/no.9441 [ ISEA], from the collection of Andrzej Górski (Bielsko- Biała, Poland); adult, male (determined based on micro-CT reconstruction). A complete specimen included in a transparent, yellow amber piece with dimensions of 7× 5 mm, maximum thickness of 2 mm. Syninclusions: numerous fungal hyphae.

Paratype: Nr. AB 058 [ CAB]; adult, sex unknown. A complete specimen with partially exposed metathoracic wings included in oval, transparent, yellow amber piece with dimensions of 39× 22 mm, maximum thickness of 6 mm; and preserved without supplementary fixation. Syninclusions: one adult Scraptiidae specimen ( Coleoptera ), and a few small stellate Fagaceae trichomes. The amber piece with the inclusion may have been thermally processed in an autoclave, based upon visible shrinking of body parts and black discoloration of syninclusions ( Hoffeins 2012).

Paratype: Nr.P 3300.138 [ RSKM]; adult, sex unknown.A complete specimen with partially exposed metathoracic wings included in transparent, yellow amber piece with dimensions of 13× 4 mm, maximum thickness of 3 mm; and preserved without supplementary fixation. Syninclusions: one very small mite specimen (Acari), and one stellate fagacean trichome .

Additional non-type material. Nr. 5726.1 [ KRAM]; adult, sex unknown. A complete specimen included in polished, transparent, yellow amber piece with dimensions of 29× 27 mm, maximum thickness of 12 mm; and preserved without supplementary fixation.Syninclusions:about 20 specimens of Nematocera ( Diptera ), one specimen of Aphidoidea (Hemiptera), one spider (Araneae), and few stellate fagacean trichomes. Specimen located in central layers of a thick amber piece, making accurate measurements and study of minute external details problematic due to distortion of visibility in the amber matrix. The specimen is similar in all visible morphological characters to MP/4233 /col. AG/no. 9441 [ ISEA], but not included in the type series.

Nr. 4298.38 [ KRAM]; adult, sex unknown. A complete specimen included in partially polished, transparent, yellow amber piece with dimensions of 36× 23 mm, maximum thickness of 10 mm; and preserved without supplementary fixation. Syninclusions: few small detrital particles. Specimen discernible in dorsal view only: antennae and legs not visible. Convex surface of the amber piece makes accurate measurements problematic. The specimen is similar in all visible morphological characters of dorsum to MP/4233 /col. AG/no. 9441 [ ISEA], but not included in the type series .

Nr. 6347 [ KRAM]; adult, sex unknown. A complete specimen, included in polished, transparent, yellow amber piece with dimensions of 46× 26 mm, maximum thickness of 11 mm; and preserved without supplementary fixation. Syninclusions: few small detrital particles, one specimen of the genus Hellenius Tobias, 1982 ( Hymenoptera : Braconidae ) [det. Dr. A. R. Manukyan], one specimen of Formicidae (Hymenoptera) , one male specimen of Chironomidae ( Diptera : Nematocera), one specimen of Acari, one adult specimen of Dasytidae (Coleoptera) . Specimen is rufous in colour and discernible in dorsal, lateral and partially ventral views, however convex surface of the amber piece and thick surrounding amber make accurate measurements and precise observation of minute details problematic. The specimen is similar in all visible general morphological characters to the holotype except for lighter colour, but not included in the type series.

Nr. 785 [ CFE]; adult, sex unknown. A complete specimen with exposed metathoracic wings included in transparent, yellow, irregular amber piece with dimensions of 17× 9 mm, maximum thickness of 3 mm; and preserved without supplementary fixation. Syninclusions: one Nematocera specimen, one exuviae of a small insect (0.56 mm long,?Thysanoptera), stellate fagacean trichomes and detrital particles. The specimen is similar in all visible morphological characters to MP/4233 /col. AG/no.9441 [ ISEA], but not included in the type series. This specimen was mentioned in Alekseev (2019) as “ Cerylonidae : Ceryloninae Billberg, 1820 (785*)”, after re-examination of the inclusion, the subfamilial identification is considered erroneous .

Type stratum. Mid-late Eocene, 48–34 Ma ( Sadowski et al. 2017, 2020; Seyfullah et al. 2018; Bukejs et al. 2019; Kasiński et al. 2020).

Type locality. Baltic Sea coast: Gdańsk, northern Poland (Holotype MP/4233 /col. AG/no.9441), and Sambian (Samland) Peninsula , Kaliningrad Region, Russia (Paratypes AB 058 and P3300.138) .

Description. Holotype MP/4233/col. AG/no.9441 [ISEA]. Measurements: body length (including head) 1.2 mm, body maximum width 0.55 mm; head length 0.24 mm, head maximum width (including eyes) 0.24 mm; pronotum length 0.27 mm, pronotum maximum width 0.50 mm; elytra length 0.72 mm, elytra maximum combined width 0.55 mm.

Body oval, slightly convex; integument unicolorous, with tarsi slightly paler (as preserved). Pubescence: head, pronotum and elytra moderately densely covered with short, erect setae; abdominal ventrites with less conspicuous semierect setation, ventrite 5 with distinctly denser setation.

Head globular, large, as long as wide; without occipital ridge or line; with distinct antennal groove at ventral margin of compound eye; densely covered with small punctation dorsally (about as large as one eye facet), distance between punctures smaller than diameter of one puncture, and with indistinct, sparse punctures ventrally. Vertex slightly convex. Frons widely impressed medially. Frontoclypeal groove not visible. Clypeus slightly convex, with rounded anterior margin. Labrum laterally not dilated beyond clypeus. Compound eyes moderately large, hemi- spherical, slightly prominent, with small, distinct facets. Antennal insertion exposed in lateral and frontal views; hidden under anterolateral margin of frons in dorsal view. Antenna clavate, consisting of 11 antennomeres, 2 terminal antennomeres forming compact, symmetrical club; short, reaching posteriorly to pronotal mid-length; sparsely setose; scape large, subcylindrical, elongate, about 1.5× as long as wide; pedicel subcylindrical, asymmetrical, narrower and shorter than scape, about 1.8× as wide as antennomere 3; antennomeres 3–7 cylindrical, elongate, slightly dilated apically; antennomeres 8–9 trapezoidal, transverse, dilated apically; antennomere 10 trapezoidal, transverse, 1.5× as wide as long, dilated apically, about 1.5× as wide as antennomere 9; antennomere 11 widely ovoid, with rounded apex, nearly as wide as long. Ratio of relative lengths of antennomeres 1–11 equal to 10:6:5:3:3:3:3:3:3:8:12. Maxillary palpi with 4 palpomeres; palpomere 1 minute, indistinctly visible in studied specimen; palpomere 2 asymmetrical, subcylindrical, nearly as wide as long; palpomere 3 transverse, slightly shorter and narrower than palpomere 2; palpomere 4 conical, slightly narrower and longer than palpomere 3, gradually tapering toward weakly rounded apex, not aciculate. Labial palpi indistinctly visible in studied specimen, apparentely with 3 palpomeres; apical palpomere conical, not aciculate gradually tapering to rounded apex. Gular suture absent.

Pronotum transverse, 1.85× as wide as long, widest within posterior one-third of its length, slightly convex, lateral surfaces explanate, lateral sulci absent. Pronotal punctation small and dense; distance between punctures equal to 0.5–1.5× diameter of one puncture, punctures smaller and sparser on disc then laterally; interspaces smooth. Lateral margins widely rounded, distinctly bordered, not crenulate; posterior margin bisinuate, with distinct medial lobe, bordered; anterior margin slightly convex in dorsal view, arcuate in frontal view, without bordering. Anterior angles almost right, slightly protruding; posterior angles obtuse, distinct. Prothoracic hypomeron flat, with sparse, large punctation, and interspaces smooth, shiny; without antennal cavities. Prosternum slightly convex, densely covered with large punctation, distance between punctures smaller than diameter of one puncture, interspaces slightly convex. Prosternal process slightly wider than procoxal diameter, slightly projecting beyond procoxae, truncate, with almost parallel lateral margins. Procoxal cavities open posteriorly; protrochantins concealed.

Scutellar shield small, oval, strongly transverse, about 2.3× as wide as long.

Elytra completely covering abdomen, ovoid, 1.3× as long as wide, widest slightly in front of middle, subparallel in anterior two-thirds and gradually narrowed in posterior one-third of length; apices rounded, confluent; anterior margin sinuate, concave medially, slightly wider than pronotal posterior margin. Elytral punctation large (larger than pronotal punctures), arranged in 10 striae (including incomplete row near scutellar shield), with striae less regular laterally and apically; distance between punctures in striae equal to 1.5–2.0× diameter of one puncture; interval flat, shiny; distance between striae about 0.5–1.5× diameter of one puncture. Epipleura wide, with sparse and small punctures, gradually narrowed posteriad, reaching elytral apex. Mesoventrite wide, with nearly flat disc, densely covered with large punctation, distance between punctures smaller than diameter of one puncture. Mesocoxal cavities widely closed laterally (externally); mesotrochantins concealed. Meso-metaventral junction straight. Metaventrite with large, dense punctation laterally, and with almost impunctate, flat disc; discrimen distinct in posterior half; postcoxal lines absent. Metepisternum parallel-sided, with oblique anterior margin, about 5× as long as wide, covered with large, dense punctation.

Legs short, covered with fine, very sparse punctures and fine, sparse, semierect setae. Procoxae globose; meso- coxae widely oval; metacoxae large, transverse, narrowly oval, 2.1× as wide as long; all coxae broadly separated: procoxae separated by 1.25× procoxal width, mesocoxae separated by 1.3× mesocoxal width, metacoxae separated by 0.7× metacoxal width. Trochanters normal, elongate, obliquely joined to femora. Femora flattened, slightly widened mesally. Tibiae thin, nearly as long as femora, slightly dilated apically; apparently without apical spurs. Tarsi long, slender, tarsomeres simple, not lobed, with sparse setation ventrally; tarsal formula 3-3-3; apical tarsomere about 2× as long as tarsomeres 1–2 combined; ratio of relative lengths of metatarsomeres 1–3 equal to 10:5:28. Pretarsal claws thin, free, simple, slightly widened basally; empodium absent.

Abdomen with 5 freely articulated ventrites; ventrite 1 longest, about as long as ventrites 2–4 combined, without postcoxal lines, intercoxal process wide with straight apical margin; posterior margin of ventrite 5 without visible crenulation; ventrite 1 with large, dense punctation laterally and at anterior margin, ventrites 2–5 with less conspicuous, small and dense punctation; sutures between ventrites 1–4 straight. Ratio of relative lengths of ventrites 1–5 equal to 25:10:7:7:10 (medially).

Aedeagus curved in lateral view; with almost parallel lateral sides; narrowed apically ( Fig. 6 ).

Paratype Nr. P 3300.138 [ RSKM]. Measurements: body length (without head) 0.93 mm, body maximum width 0.55 mm; pronotum length 0.24 mm, pronotum maximum width 0.47 mm; elytra length 0.69 mm, elytra maximum combined width 0.55 mm. Metathoracic wings developed. Otherwise, this specimen is similar in all visible morphological characters to holotype MP/4233 /col. AG/no.9441 [ISEA].

Paratype Nr. AB 058 [ CAB]. Measurements: body length (without head) 0.92 mm, body maximum width 0.53 mm; pronotum length 0.24 mm, pronotum maximum width 0.46 mm; elytra length 0.68 mm, elytra maximum combined width 0.53 mm. Pubescence less conspicuous. Metathoracic wings well developed. Otherwise, this specimen is similar in all visible morphological characters to holotype MP/4233 /col. AG/no.9441 [ISEA].

Etymology. The epithet of the new species is based upon the Greek adjective “πάνδημος” or “ pandemus ”, meaning “pertaining to all the people, public” or “epidemic, occurring on a scale that crosses international boundaries”, and it refers to the international character of the present study including workers from three continents, and the global pandemic of coronavirus (i.e., COVID-19).

Figures

FIGURE 1. Protostomopsis pandema gen. et sp. nov., holotype, No MP/4233/col. AG/no. 9441 [ISEA]: A, B – dorsal habitus photomicrograph, and corresponding X-ray μCT rendering; C, D – ventral habitus photomicrograph, and corresponding X-ray μCT rendering. Scale bars represent 0.25 mm.

FIGURE 2. Protostomopsis pandema gen. et sp. nov., holotype, No MP/4233/col. AG/no. 9441 [ISEA] surrounded by fungal hyphae: A, B – right lateral habitus photomicrograph, and corresponding X-ray μCT rendering; C, D – left lateral habitus phot- omicrograph, and corresponding X-ray μCT rendering. Scale bars represent 0.25 mm.

FIGURE 3. Protostomopsis pandema gen. et sp. nov., paratype, No P3300.138 [RSKM], habitus: A – dorsal view; B – ventral view; C – right lateral view. Scale bar represents 0.5 mm.

FIGURE 4. Protostomopsis pandema gen. et sp. nov., paratype, No P3300.138 [RSKM]: A – habitus, ventrolateral view; B – details of abdomen showing apical margin of ventrite 5. Scale bars represent 0.5 mm for Fig. A, 0.1 mm for Fig. B.

FIGURE 5. Protostomopsis pandema gen. et sp. nov., paratype, No AB 058 [CAB]: A – habitus, dorsal view; B – habitus ventral view; C – right metathoracic wing, ventral view. Scale bars represent 0.25 mm for Figs. A and B, 0.1 mm for Fig. C.

FIGURE 6. Protostomopsis pandema gen. et sp. nov., MP/4233/col. AG/no.9441 [ISEA], X-ray μCT rendering of aedeagus:A – dorsal view; B – ventral view; C – lateral view. Abbreviations: ap—apex; ba—base. Scale bar represents 0.1 mm.