Siphloplecton sp. 5

Godunko, Roman J., Neumann, Christian & Staniczek, Arnold H., 2019, Revision of fossil Metretopodidae (Insecta, Ephemeroptera) in Baltic amber - Part 4: Description of two new species of Siphloplecton Clemens, 1915, with notes on the new S. jaegeri species group and with key to fossil male adults of Siphloplecton, ZooKeys 898, pp. 1-26 : 1

Siphloplecton sp. 5 Figures 12 , 13 ; Table 1

Material examined.

Male imago in Baltic amber (Eocene), CCHH, BaB Nr. 1159/5. A generally completely preserved specimen, well visible in dorsoventral aspect in translucent amber ( Fig. 12 A–B ). Some resin influxes around specimen. Right foreleg and right cercus lost. Dorsal side of body only with several very small spots of “Verlumung”. Ventral side of head, thorax and, partly, abdominal sterna intensively covered with “Verlumung”. For this reason, some aspects of mesosternum and the shape of the genitalia are poorly visible. One female nonbiting midge ( Diptera : Chironomidae ) is embedded in the same stone.

Relatively pale specimen, yellowish to brown. Wings with artificial, irregular dark spots; distal portions of forewings and right hind wing with distinct concentration of such spots ( Fig. 12E ). Legs uniformly coloured. For measurements see Table 1 .

Description.

Head light brown. Eyes large, slightly flattened, pale, dirty yellowish. Several brownish spots on eye surface. Ocelli and antennae of same colouration as head, completely preserved; antennae slightly longer than head ( Fig. 12C, E ).

Thorax with traces of brownish pigmentation on dorsal and ventral sides, brown. Pronotum well preserved. Arrangement of thoracic sutures on dorsal and ventral sides of mesothorax typical for Siphloplecton ( Figs 12 C–D , 13 ). Most of head and thorax ventrally covered with “Verlumung”. Lateral aspect of thorax hardly visible.

Wings basally translucent, hyaline, with well visible longitudinal and transversal venation. Pterostigmatic area hyaline, opaque, with several anastomosed veins. Cubital field of forewings with well visible pair of intercalary veins connected with CuA, and one additional, well developed vein also directed toward CuA ( Figs 12 E–G , 13 ). Hind wings with triads RS, MA and MP, 0.36 × forewing length; costal process bluntly pointed and small ( Figs 12E , 13 ).

Legs yellowish to light brown. Several pointed spines at outer margin of foretibia. Characteristics of legs similar to those of other representatives of Siphloplecton . Measurements of leg segments in Table 1 .

Abdominal segments completely preserved; abdominal terga slightly paler than sterna.

Styliger plate only partly visible, most of styliger base covered with “Verlumung”. Thus, shape of styliger projections not clearly visible ( Fig. 12H ). Basal segment of forceps basally not widened, distinctly narrower than adjoining apical part of plate (character well visible only in right clasper); forceps 4-segmented, segment 4 approximately 3.20 times longer than wide; length ratio of segment 3 to segment 4 approximately 1:1 ( Fig. 12H ).

Penis lobes covered with “Verlumung” (especially left lobe); penis lobes elongated, relatively narrow and separated from each other apically; medial sclerite rounded apically; lateral and medial sclerites probably separated on outer side (poorly visible) ( Fig. 12H ).

Paracercus vestigial, at least 3-segmented; left cercus slightly damaged; right cercus lost.

Comments.

This species is closely related to S. landolti sp. nov. due to the similar proportions of the forceps segments and shape of the penis lobes, especially the apical portion of the medial sclerite, and the presence of 2+1 intercalary veins in the cubital field of the forewings. This last character also confirms the inclusion of Siphloplecton sp. 5 within the S. jaegeri species group. At the same time, we could not confirm its conspecificy with Siphloplecton landolti sp. nov. or other species, since the details of the male genitalia are poorly visible.

Figures

Figure 12. Siphloplecton sp. 5, CCHH, BaB 1159 / 5, male imago (photographs) A general dorsal view B general ventral view C head and thorax in dorsal view D head and thorax in ventral view E base of right forewing and hind wing in ventral view F left forewing in ventral view G cubital field of left forewing in ventral view H genitalia in ventral view.

Figure 13. Siphloplecton sp. 5, CCHH, BaB 1159 / 5, male imago (line drawing): general dorsal view of body, right forewing, left and right hind wings.