Eonandeva Giłka et Zakrzewska, 2015

Zakrzewska, Marta & Giłka, Wojciech, 2015, Eonandeva gen. nov., a new distinctive genus from Eocene Baltic amber (Diptera: Chironomidae), Zootaxa 4044 (4), pp. 577-584 : 578

Genus: Eonandeva Giłka et Zakrzewska , gen. nov.

Type species: Eonandeva helva Giłka et Zakrzewska sp. nov. (present designation). Other species: Eonandeva latistyla Giłka et Zakrzewska sp. nov.

Derivatio nominis. We believe this Eocene genus is closely related to the extant Nandeva .

Diagnosis. Adult male. Eonandeva is treated as a possible member of the tribe Tanytarsini showing the RM vein as a continuation of M and R4+5 or slightly oblique relative to them, the bare squama and the strongly reduced anal area of the wing with the anal lobe not developed. The new genus differs from all other genera of the tribe, including the presumably closest genus Nandeva , in the shape of the gonostylus, which bears a subapical flattened lobe on the median margin and a stout, strongly elongated and more or less parallel-sided superior volsella.

Description. Adult male.

Small species, wing length c. 800–900 Μm. Eyes bare, reniform, without dorsomedian extensions, broadly separated by frons. Antenna with 13 flagellomeres, AR c. 0.7, plume well developed. Frontal tubercles absent. Palp fully developed, 5-segmented. Clypeus with several (4–6) setae placed in row in proximal part. Thorax with dorsocentral setae arranged in small field anteriorly, 6 prealar setae in roundish field. RM vein as continuation of M and R4+5 or slightly oblique relative to them, R4+5 ending distally of M3+4 towards tip of wing; squama bare; anal lobe not developed ( Fig. 1 C, D; 3C). Mid and hind leg tibia with two minute well separated combs, at least one comb bearing spur. Pulvilli absent. Gonostylus longer than gonocoxite, with subapical flattened lobe on median margin ( Fig. 2 , 4 ). Anal point styliform, slender, reaching far beyond apices of superior volsellae. Superior volsella stout, strongly elongated, parallel-sided, apically rounded ( Fig. 2 D, 4D). Digitus and median volsella not developed. Inferior volsella with enlarged apical part.

Figures

FIGURE 1. Eonandeva helva sp. nov., adult male, holotype CCHH 1754 – 1 (Eocene, ~ 45 – 40 Ma; Baltic amber, Gulf of Gdańsk). A — inclusion in amber; B — habitus; C — wing; D — RM vein area of wing.

FIGURE 2. Eonandeva helva sp. nov., adult male, holotype CCHH 1754 – 1 (Eocene, ~ 45 – 40 Ma; Baltic amber, Gulf of Gdańsk). Hypopygium and its structures in dorsal (A – D) and ventral aspect (E), photographed in reflected light (A), in transmitted light (E) and drawn (B – D); C — distal part of gonostylus; D — superior volsella (C and D magnified c. 2 times relative to B).

FIGURE 4. Eonandeva latistyla sp. nov., adult male, holotype CCHH 1754 – 10 (Eocene, ~ 45 – 40 Ma; Baltic amber, Gulf of Gdańsk). Hypopygium and its structures in dorsal aspect, photographed in reflected light (A) and drawn (B – D); C — distal part of gonostylus; D — superior volsella (C and D magnified c. 2 times relative to B).