Galloatherix completus, Grimaldi, 2016

Grimaldi, David A., 2016, Diverse Orthorrhaphan Flies (Insecta: Diptera: Brachycera) In Amber From The Cretaceous Of Myanmar: Brachycera In Cretaceous Amber, Part Vii David A. Grimaldi, Bulletin of the American Museum of Natural History 2016 (408), pp. 1-132 : 39-42

Galloatherix completus , new species

Figures 13 , 46

DIAGNOSIS: Distinguished from G. incompletus Nel et al. by the wing of G. completus having vein R 2+3 less sinuous; cell d slightly longer, veins M 1, M 2, and M 3 shorter (fig. 11D).

DESCRIPTION: Based on male and female. Male (paratype), female holotype, respectively: body length 3.64, 4.79 mm; thorax length 1.24 mm, (female not measured); abdomen length 1.83, 2,59 mm; wing length 2.48, 4.17 mm; proboscis length 0.52, 1.46 mm. FEMALE: Head: Eyes large, somewhat anteroposteriorly flattened, frontal surface broad; in lateral view occiput not visible posteriorly. Facets not differentiated; eye almost bare, with sparse, very fine, short setulae. Medial margins distant along frons, nearly parallel, width approximately equal to distance between outside margins of antennal bases. Frons with fine, short, sparse setulae (appears to have transverse striae, but these are probably artifactual). Ocelli on low tubercle; vertex with short, stiff setae. Occiput not visible. Face with large, bulbous clypeus; clypeus bare, roughly pear shaped, with broad, more bulbous end dorsally; clypeus bordered laterally by extensive membranous area and then more laterally by deep grooves/sulci. Antenna: Basal 3 segments short, compact; apical antennal article aristate. Antennal base with small, shelflike lobe dorsally; scape cylindrical, with deeply incised lateral and medial areas; pedicel short, squat, apical surface conforming to proximal surface of flagellomere 1; scape and pedicel with short, stiff setae. Flagellomere 1 reniform, connected to pedicel at middle of flagellomere. Apical flagellar article long, fine, aristalike, with minute pubescence. Presence of minute apical style not observable. Mouthparts: Proboscis long, fortuitously separated from labium and labellum in holotype specimen. Proboscis significantly longer than head depth: depth of head 1.0 mm, length of exposed part of proboscis 1.46 mm (labium slightly shorter). Labium broad and shallow basally, apically narrowed to (at labellum) 0.5× basal width; dorsal longitudinal groove not separate on labellum, gradually separated and widened basad; labium bare of setae; labellum with fine, stiff setae. Labellum 0.2× length of theca. Mandibles present, flat, long, swordlike, tips sharp but not finely serrate; lacinia slightly thinner than mandible, flattened and swordlike, tip sharp and with minute serrations. Labrum long and slen- der. Palp long, slender, gently curved (dorsally convex), slightly tapered in thickness distad; 2-segmented, basal segment short, 0.37× length of distal segment; apical segment with short, stiff setae on dorsal and ventral surfaces. Thorax: Right side of holotype preserved as hollow impression within interior of amber piece, revealing details; left side and scutellar area entirely lost. Dorsum of mesonotum with short, stiff, erect setae; notopleural area with slightly longer setae; pleurites entirely bare. Wing: Moderately long and slender, W/L 0.37, hyaline except for small pterostigmatic area between apices of veins R 1 and R 2+3; 1–3 rows of minute setulae/microtrichia on dorsal surfaces of bases of R 1 and Rs and stem of Cu; longest setulae at stem of vein R + Sc. Basicosta a slender, deeply excised lappet. Vein C circumambient, significantly thinned at apex of wing, with very fine stiff setulae. Sc 0.53× length of wing; R 1 0.63× length of wing; R 2+3 not sinuous, apex of R 2+3 converging toward and very close to apex of R 1, but not meeting; stem of R 4-5 thickest vein after C; fork of R 4+5 arising slightly distal to distal end of cell d. Cell d straight, not curved; length of d greater than veins M 2 and M 3, shorter than M 1; M 1 slightly sinuous. Cell br 1.45× length of cell bm; apices of M 3 and CuA 1 distant, not converging, meet wing margin; apices of CuP and A 1 not preserved (cannot determine whether forming cup cell). Anal lobe present but small, alula well developed but more shallow than upper calypter, upper calypter subcircular. Legs: Long, slender. Femora setulose, especially dorsally. Ventral surface of profemur with minute tubercle near middle, bearing 4–5 long, fine, stiff setae that point distad. Tibiae and tarsi with dense vestiture of setulae. Tibial spurs 1-2- 2, long, lengths greater than apical widths of respective tibiae. Dorsal surface of metatibia and ventral surface of all basitarsi with short, stout spinulelike setae. Empodium pulvilliform, broader than pulvilli. Abdomen: Not dorsoventrally flattened, with large membrane between tergites and sternites. Sternites large, bare. Tergites with vestiture of dense, short, erect, and decumbent setae. Cerci 2-segmented, shape of basal segment not observable.

MALE: Very similar to female with differences as follows: Head: Anteroposteriorly flattened, with eyes fully frontal and occupying nearly entire frontal surface of head. Eyes holoptic in middle portion of frons, medial margins divergent ventrally and dorsally. Facets differentiated in size: inner halfdiameter of eye with larger facets, grading laterally to smallest facets laterally; lateralmost facets with diameter ca. 0.5× that of medial facets. Frons dorsal to antennae with short, fine pubescence. Ocelli large, on low tubercle; tubercle with thick stiff, stout setae. Occiput with thick, short, stiff setae. Clypeus small, bulbous, with deep sulci laterally (no membranous areas); bare. Antenna: Flagellomere 1 connected to pedicel near dorsal end of flagellomere (vs. at middle). Mouthparts: Proboscis short, length slightly greater than 0.5× depth of head capsule; labellum equivalent in size to that of female. Palp more slender than in female, digitiform, even in width throughout (not apically tapered); with stiff setae on ventral surface only. Thorax: Wellpreserved in male, including color pattern. Mesono- tum largely dull brown, with pair of light, incomplete, paramedian stripes thickened in width along transverse suture and at base of stripe. Notum dorsally with dense vestiture of thick, decumbent setulae, longer, finer setae laterally (on supraalar region, scutellar margin). Legs: Hind femur with ventral row of long, fine, erect setae on distal half. Abdomen: Moderately dorsoventrally flattened; tergites and sternites broad, pleural membrane between them not exposed. Tergites with denser, longer setae than in female.

TYPES: Holotype, female, AMNH Bu-SE2/5a. Paratype, male, in same piece as female, AMNH Bu-SE2/5b.

ETYMOLOGY: Named as a contrast to the type species, G. incompletus , which is known only as a wing; G. completus is known from the bodies of both sexes as well as wings.

COMMENTS: Fortuitously, the male and female are preserved in the same piece of amber, a flattened, ovoid, clear yellow piece 23 × 11 × 3 mm. Conspecificity of the two individuals is reflected by the matching wing venation, the detailed structure of the antenna and palp, and other aspects of the general morphology. In fact, the two individuals were probably in copula just prior to capture in amber since the abdominal tips of the flies oppose each other very closely (fig. 46) (the male terminalia were ground off at the surface of the amber prior to acquisition; female terminalia are intact and not coupled). What is most striking is the sexual dimorphism in the length of the proboscis, with that of the female nearly three times that of the male. I am unaware of any living tabanomorphs where there is such dramatic sexual dimorphism in mouthparts.

Figures

FIG. 13. Galloatherix completus, new species (stem-group Tabanomorpha), AMNH Bu-SE2/5a. A, C, D. Female holotype, AMNH Bu-SE2/5a. B. Male paratype, AMNH Bu-SE2/5b. A. Wing. B. Male head, oblique lateral view. C, D: Female mouthparts, with labium and labellum separated from remainder. Panels B−D to the same scale.

FIG. 46. Galloatherix completus, new species (stem-group Tabanomorpha), female holotype and male paratype AMNH Bu-SE2/5a, b. A. Habitus of female (above) and male (below), shown as preserved (in or near copula). B. Head and thorax of female holotype, frontolateral view. C. Head and thorax of male paratype, lateral view.