Myanmaro primus, Giłka & Makarchenko & Pankowski & Zakrzewska, 2019

Giłka, Wojciech, Makarchenko, Eugenyi A., Pankowski, Mary K. & Zakrzewska, Marta, 2019, Myanmaro primus gen. et sp. nov., the first orthoclad (Diptera: Chironomidae) from Cretaceous Burmese amber, Zootaxa 4565 (1), pp. 61-70 : 63-67

Myanmaro primus sp. nov.

Figures 2–4

Type material. Holotype, inventory no. F1a LSZ DIZP: adult male (complete specimen, thorax deformed, Fig. 2A, B ) preserved in 11.5 x 8.5 x 3 mm piece of Burmese amber (mid-Cretaceous, ~100 Ma, IR spectrum no. 13998 IAA, Fig. 1 ) mined in Hukawng Valley , Kachin State, Myanmar. Syninclusion: Chironomidae adult (inventory no. F1b LSZ DIZP).

Derivatio nominis. This is the first described representative of the chironomid subfamily Orthocladiinae from Cretaceous Burmese amber.

Diagnosis. As for the genus.

Description. Adult male (n = 1, holotype).

Total length ~ 2.2 mm. Wing length: ~1185 µm. Total length/wing length ratio ~1.85.

Colouration. Body, including antenna, legs and haltere dark brown to black. Wing membrane yellowish, hyaline; C, M and radial veins distinctly darker, brown.

Head ( Fig. 2B, C ). Eyes bare, with bluntly wedge-like dorsomedian extension. Antenna with 13 weakly discernible flagellomeres, proximal flagellomeres incompletely fused ( Fig. 2C ), ultimate flagellomere 468 µm long, AR ~1.3; pedicel pubescent, plume well-developed. Clypeals at least 12, numerous on clypeus margin. Length of palpomeres 3–5 (µm): ~75, 70, 130 (proximal palpomeres unobservable).

Thorax chaetotaxy. Aps 5–6 on each side laterally; Ac 4 pairs at least, minute; Dc 25 at least on each side, bi- or multiserial; Scts 4 at least; Pa 1 at least on each side, bristle-like. Postnotum bare. Other setae unobservable due to deformation of thorax.

Wing ( Fig. 2 D–F). Fully-developed, ellipse-shaped ( Fig. 2D ), with anal lobe distinct ( Fig. 2E ). Veins ending as follows (in order from base to tip): An and Sc (distal sections fading), Cu 1, R 1, R 2+3, M 3+4, R 4+5, M 1+2; FCu under RM; An reaching FCu at most. VR C ~2.2. VR Cu ~1.1. Setae present only on wing margin incl. costa, other veins bare. Brachiolum with several setal tubercles (1 long seta preserved). Squama with 10 setae ( Fig. 2E ). Wing membrane without setae, but with fine punctation forming an ornament, as shown on Fig. 2F .

Legs ( Figs 2B , 3 A–H). Tibial combs absent. Spurs and pseudospurs smooth, straight or slightly curved. Fore leg tibia with short spur (12–15 µm) ( Fig. 3A, B ); mid leg tibia with two spurs (15 and 25 µm long) ( Fig. 3C ); hind leg tibia with two unequally long spurs (25 and 40 µm long) and shorter (~20 µm) pseudospur between ( Fig. 3D ). Pseudospurs on mid leg tarsomeres 1–4 arranged as follows: ta 1 with 2 pseudospurs ( Fig. 3E ), ta 2: 1 ( Fig. 3F ), ta 3: 1 ( Fig. 3G ), ta 4: 3 pseudospurs ( Fig. 3H ); pseudospurs on tarsomeres of fore and hind legs absent. Pulvilli absent. Claws simple, strongly curved apically. For length of leg segments and leg ratios see Table 1.

Hypopygium ( Fig. 4 A–E). Tergite IX extensive, with membranous posterior shoulders surrounding subtriangular anal point, and longitudinal double keel diverging into median pit with two minute protuberances and ribs running towards anal point apex; anal point broad at base, with membranous lateral parts and well-pigmented median section, as show in Fig. 4A, B, D . Gonocoxite ~205 µm long, slender but slightly swollen in proximal section, with two setae placed near apex ventrally. Gonostylus bifurcate: main branch ~75 µm long, curved at mid length, with slightly broadened distal section, apex beak-shaped bearing 2 short subapical setae, megaseta absent; inner branch ~25 µm long, thumb-shaped, without setae, connected by distinct articulation with main branch ( Fig. 4 A–C). Inferior volsella ~70 µm long and 35 µm wide, with head-like dorsal part and extensive ventral lobe covered with dense protuberances and setae ( Fig. 4A, B, E ). HR ~2.7, HV ~2.9.

Figures

FIGURE 1. IR (ATR) spectrum (no. 13998 IAA) obtained from examined amber (mid-Cretaceous Burmese amber, ~100 Ma; Hukawng Valley, Kachin State, Myanmar).

FIGURE 2. Myanmaro primus sp. nov., holotype, adult male (F1a LSZ DIZP, mid-Cretaceous Burmese amber, ~100 Ma; Hukawng Valley, Kachin State, Myanmar): A inclusion in amber, B habitus, C head and antenna (white arrows: borders between flagellomeres, grey arrow: incomplete fusion), D wing, E base of wing, F punctation of wing membrane below RM area. Scale bars: 5 mm (A), 1 mm (B), 100 µm (C–F).

FIGURE 3. Myanmaro primus sp. nov., holotype, adult male (F1a LSZ DIZP, mid-Cretaceous Burmese amber, ~100 Ma; Hukawng Valley, Kachin State, Myanmar): A–D tibial spurs of fore (A, B), mid (C) and hind leg (D); E–H pseudospurs of mid leg tarsomere 1 (E), 2 (F), 3 (G) and 4 (H). Scale bar: 10 µm.

FIGURE 4. Myanmaro primus sp. nov., holotype, adult male (F1a LSZ DIZP, mid-Cretaceous Burmese amber, ~100 Ma; Hukawng Valley, Kachin State, Myanmar). Hypopygium in dorsal (A) and ventral view (B), C gonocoxite (grey) and gonostylus (blue) with articulate lobe (green), D distal part of anal tergite and anal point, E inferior volsella. Scale bars: 50 µm (A, B), 25 µm (C–E).