Tanytarsus glaesarius Giłka et Zakrzewska, 2015

Zakrzewska, Marta & Giłka, Wojciech, 2015, The Tanytarsini (Diptera: Chironomidae) in the collection of the Museum of Amber Inclusions, University of Gdańsk, Zootaxa 3946 (3), pp. 347-360 : 353-356

publication ID	https://doi.org/ 10.11646/zootaxa.3946.3.3
publication LSID	lsid:zoobank.org:pub:8D7575DB-636C-4473-91C3-A58C1E5F9E73
DOI	https://doi.org/10.5281/zenodo.5616328
persistent identifier	https://treatment.plazi.org/id/03CD3E7A-7111-A71B-FF60-A89CD0CCF0D5
treatment provided by	Plazi
scientific name	Tanytarsus glaesarius Giłka et Zakrzewska
status	sp. nov.

Treatment

Tanytarsus glaesarius Giłka et Zakrzewska View in CoL , sp. nov.

Type material. Holotype. Adult male (tarsi of left fore and hind leg missing, tarsi of mid legs broken and separated) preserved in 21 x 13 x 1 mm piece of amber (Eocene, ~45–40 Ma, Baltic amber, Gulf of Gdańsk; MAI- 415a; Fig. 5 View FIGURE 5 A); animal syninclusions: Ceratopogonidae , Formicidae , Mordellidae, Thysanoptera, Psocoptera (all as single ind., MAI-415).

Derivatio nominis. Adjective derived from the Latin noun ‘ glaesum ’, amber.

Diagnosis. Frontal tubercles stout, cylindrical. Antenna with flagellomeres 10–11 fused in part and 12–13 completely fused. Wing vein FCu placed far distally of RM (VR Cu 1.52). Anal point wide at base, distinctly narrowed subapically, tapering to pointed apex. Superior volsella with 2 setae on apex. Digitus long, extending beyond superior volsella, curved, with blunt apex. Stem of median volsella bulbous, with slender foliate lamellae.

Description. Adult male (n = 1)

Total length c. 1.2 mm; wing length c. 820 Μm.

Head ( Fig. 5 View FIGURE 5 C–E). Eyes bare, reniform, with dorsomedian extensions ( Fig. 5 View FIGURE 5 C). Frontal tubercles stout, cylindrical with blunt apices, c.15-20 Μm long ( Fig. 5 View FIGURE 5 D). Antennal flagellum composed of 11 segments of which 10 are well discernible, flagellomeres 10–11 fused in part (borders between remaining flagellomeres not visible, but distribution of setal tubercles indicates 13 segments), AR 0.82 (when flagellum measured as 10-segmented), AR 0.65 (as 11-segmented); plume fully developed (setae separated, but setal tubercles well developed) ( Fig. 5 View FIGURE 5 E). Length of palpomeres 2–5 (Μm): c. 30, 60, 76, 129. At least 15 clypeals.

Thorax. Ac and Dc not visible (thorax damaged in dorsal part), Pa 3 on each side, Scts 6 at least.

Wing ( Fig. 5 View FIGURE 5 F). Slender, with anal lobe weak, broadest at 2/3 length, width: 260 Μm, length/width ratio 3.15. FCu placed far distally of RM; VR Cu 1.52. Veins ending as in most extant Tanytarsus (from base to tip): An, Sc, Cu1, R1, R2+3, M3+4, R4+5, M1+2; distances between ends of R1–R2+3 and R2+3–R4+5 unequal (VR C c. 2.15). Almost whole wing (except base) covered with dense macrotrichia.

Legs. Tibia of fore leg without spur. Tibial combs of mid and hind legs separated, fan-shaped, teeth up to 16 Μm long; each comb with slender spur, 26 Μm long (mid leg) and 20–32 Μm long (hind leg). Sensilla chaetica on ta1 of p2 not observed. Lengths of leg segments and leg ratios in Table 2 View TABLE 2 .

Hypopygium ( Fig. 6 View FIGURE 6 A–E). Gonostylus stout, slightly arcuate, c. 50 Μm (as long as gonocoxite), with sparse setae placed on median margin in distal half. At least 2-3 tubercles bearing posterolateral setae on each side of anal point. Anal point wide at base, distinctly narrowed subapically, tapering to pointed apex; spinulae or crests unobservable from ventral side. Superior volsella (visible only in distal part) with 2 setae on apex; digitus long, extending beyond superior volsella, curved, with blunt apex ( Fig. 6 View FIGURE 6 D). Stem of median volsella bulbous, c. 15 Μm long, with 3 slender foliate lamellae ( Fig. 6 View FIGURE 6 E). Inferior volsella reaching half length of gonostylus, stout, with slightly swollen apical half posteromedially directed, armed with several curved setae on apex and strong setiform microtrichia on posterolateral margin ( Fig. 6 View FIGURE 6 A–C).

Remarks. A set of characters given in the diagnosis and description (except the number of antennal flagellomeres, see remarks below), indicate that the new species belongs to the genus Tanytarsus . Several significant characters, i.e. the shape of the hypopygial superior volsella (with 2 setae on apex), the digitus (long, extending far beyond superior volsella), and the median volsella (with stout bulbous stem and slender foliate lamellae) are known from species of different systematic groups, e.g. the eminulus- mendax - or chinyensis group (cf. Reiss & Fittkau 1971, Ekrem 2003, Giłka & Paasivirta 2009). However, these characters form a combination unknown from any extant or fossil Tanytarsus , thus a group membership of Tanytarsus glaesarius remains open. Tanytarsus glaesarius is the first Eocene species of this genus known from the adult male having the antenna with the reduced number of flagellomeres ( Fig. 5 View FIGURE 5 E). This character is similar to that discussed above (see remarks on Stempellinella electra ), but we propose to weigh it differently on a background of all known Tanytarsus , including extant species of this genus (males with 13 flagellomeres). Since we have not observed other characters that might suggest non-typical structure (e.g. deformations, asymmetry, brachyptery or other associated features known from non-flying chironomids; cf. Giłka 2011b, Giłka et al. 2013a), we assume that the reduced number of flagellomeres observed in T. glaesarius should be treated as a species-specific feature rather than a character which might be considered in the context of phylogenetic trends.