Myanmyia asteiformia Grimaldi

Grimaldi, David A., Arillo, Antonio, Cumming, Jeffrey M. & Hauser, Martin, 2011, Brachyceran Diptera (Insecta) in Cretaceous ambers, Part IV, Significant New Orthorrhaphous Taxa, ZooKeys 148, pp. 293-332 : 323

Myanmyia asteiformia Grimaldi sp. n. Fig. 11

Diagnosis.

As for genus.

Description.

Body size small, length 1.35 mm (excluding antennae and cerci), slender. Wing length 1.05 mm. Head: Slightly wider than thorax [possibly preservational, as head is slightly compressed]. Antenna with cup-like pedicel, distal edge rimmed with fine, stiff setae; basal flagellomere drop-shaped, width approximately equal to length; arista-like stylus terminal, setulose, 1-articled (no small basal articles), length approximately 3 × length of basal flagellomere. Eyes large (occupying virtually entire lateral surface of head), bare, with slight dorsoventral differentiation of facets (dorsal facets ca. 2 × diameter of ventral ones); inner margins of eyes (on frons) very close, width of separation equal to ca. 3 facet diameters. Ptilinal suture absent. Maxillary palp 2-segmented, with apical segment clavate and basal segment slender. Labrum long, very slender; hypopharynx (?) stylet-like; labellum small. Gena very shallow or barely developed (not apparent). Postocciput broad, concave. Thorax: Slender, with the following dorsal setae (per side): 1 postpronotal, 4 supra-alar/notopleurals, 3 postsutural dorsocentrals (posterior one largest), 2 pairs scutellars [pleura not visible]. Legs of moderate length, setulose, without distinctive spines/spurs. Pretarsus with claws well developed, but no pulvilli. Wing: Long, slender, W/L = 0.33; membrane microtrichia arranged in oblique rows (between R veins) and longitudinal rows (portions of space between R4+5 and M). Vein C slightly beyond apex of R4+5, no humeral or subcostal breaks; with long, sparse spinules. Sc short, very faint [best seen when tilting specimen]. Base of vein R thick, R1 short (length 0.3 × length of wing); R2+3 unbranched, meeting C at ⅔ the length of wing. R4+5 straight, extended to tip of wing, unbranched. Vein M simple, unbranched, very lightly sclerotized; both ends evanescent. Sc. Vein A thick, heavily sclerotized strip along alular edge of wing. Anal lobe and alula not developed. Halter: with large, darkened knob, stem approximately same length as knob or slightly longer. Abdomen: Tergites I-VII well developed, with sparse setulae, without macrosetae; sternites II, III, IV large, bare; segment V is tubular; VI, VII ring-like; terminal segment bearing pair of long, finger-like, one-segmented cerci. Presence/absence of abdominal muscle plaques not visible.

Type.

Holotype, female, AMNH Bu1616, in amber from northern Myanmar: Kachin State, Tanai Village, 105 km NW Mytikyina. The holotype is the sole inclusion in a clear amber-colored piece 9 × 6 × 2 mm. Ventral surface of the thorax and the abdomen are compressed, and a crack through the thorax obscures some details. The left wing of the unique specimen is well preserved, but venation is optimally observed by tilting and observing the piece at various oblique angles. Right wing is twisted, but in oblique view additional details of venation are visible.

Etymology.

L., for like, and Asteia (type genus of the Asteiidae , a family of Schizophoran flies) and Latin -formia, meaning like, in reference to the similarity of the unrelated two taxa in body shape, size, and wing venation.