Chimeromyia mediobscura Grimaldi & Cumming

Grimaldi, David A., Cumming, Jeffrey M. & Arillo, Antonio, 2009, Chimeromyiidae, a new family of Eremoneuran Diptera from the Cretaceous, Zootaxa 2078, pp. 34-54 : 40-48

Chimeromyia mediobscura Grimaldi & Cumming , sp. n.

( Figs. 5–8 )

Diagnosis. Base of M (proximal to crossveins r-m and m-cu) virtually lost, fold-like; R2+3 gradually tapered toward C (not abruptly turned); crossveins r-m and bm-cu contiguous or nearly so, but interrupted where M intersects; anal lobe barely evident, no alula, a small spur of a vein at base of wing (CuA2 + CuP); two pairs of scutellar setae (posterior pair cruciate); arista dorsal; male: surstylus simple and digitiform, postgonites spatula-shaped, hypandrium cleft with apices of lobes pointed, stVIII with row of large setae on apical margin; female terminalia: simple, tapered to narrow apex, cerci present. In Lebanese amber.

Description. A small, bristly species, slightly more robust than other Chimeromyia. HEAD: Wider than long; eyes large, bare, facets not differentiated. Ocellar triangle on small, slightly raised tubercle, with 2 long pairs of ocellar setae; posterior ocellars 0.7x length of anteriors. Pair of long vertical setae, nearly erect; 4–5 postoccipital setae very close to posterior margin of eye. Antenna with flagellomere I setulose, rounded; arista situated near dorsal margin; 3 aristal articles, basal two aristomeres minute, approximately equal in length. Clypeus protuberant; with pair of facial setae present, projecting anteriad, length 0.5x that of anterior ocellar setae. Palpus and labellum small; labrum visible in one specimen (Az285), length c. 3x the width, with pointed apex. Epipharyngeal teeth, if present, not visible. THORAX: Fairly broad, setose. Scutum with one row 6–8 acrostichal setulae; pair of large dorsocentral setae between supra-alars, ca. 5 small dorsocentrals in each row; two supra-alar setae present, two notopleural setae; one erect postpronotal seta; scutellum with apical pair of long, cruciate setae, subapically with smaller, finer pair, 0.7x length of apicals. Legs long, femora stout (particularly hind femora). Femora with ventral row of ca. 4–6 stiff, fine setae, lengths about equal to width of femur. Legs largely yellowish, apical two tarsomeres dark brown to blackish, very dark in fore tarsi. Hind tibia of male without plumosity, but with dorsal and ventral row of short, stiff setae ( Fig. 5 b).

Wing with vein C extended to apex of M1; Sc incomplete, apex evanescent, crossvein h not present; R1 meeting C near middle of wing; R2+3 nearly straight, sloped gradually toward C; vein R4+5 forked with R4 and R5 widely divergent, length of fork significantly less than base of fork; base of M (proximal to r-m and m-cu) fold-like, virtually absent; M1 parallel to base of fork R 4+5; crossveins r-m and bm-cu in line, sometimes with slight break where they would meet M; vein M2 thin, almost connected distally to wing margin, proximal end evanescent; CuA1 tapered, small spur of a vein (CuA2 + CuP) present at base of vein; although anal lobe present but highly reduced. ABDOMEN: Slender, with male genitalia projected posteriad, not dorsoflexed. Male terminalia: Cerci fused at base, narrow and slightly cleft apically, formed hood-like over phallus and surstyli. Surstyli long, simple lobes with 4–5 small setulae at apex; lengths approximately equal to that of phallus. Phallus narrow, apically scoop-shaped; postgonites laterally flat and spatula-shaped, with stiff apical setae on ventral margin, length slightly less than that of phallus. Hypandrium largely hidden by large sternite VIII; apex of hypandrium cleft, with apex of both lobes pointed. Sternite VII with row of ca. 10 large, stiff setae near apical margin. Female terminalia: simple, tapered to narrow apex with cerci present.

Types. All types in Lebanese amber. Holotype, male, Az649; Paratypes: male, Az440; male, 274; female, Az285. All in MHNP.

Etymology. In reference to the median vein and its faint structure.

Chimeromyia pilitibia Grimaldi & Cumming , sp. n. ( Figs. 9 , 10 )

Diagnosis. Antennal arista dorsal, not apical; crossvein bm-cu slightly proximal to r-m, not directly in line; base of vein M sclerotized (not evanescent), bisecting cells br and bm; R2+3 abruptly upturned toward C; two pairs scutellar setae, posterior pair cruciate; hind tibia plumose (probably in males only), with 3–4 longitudinal rows of long, fine setae; male terminalia with bilobed (vs. simple) surstylus.

Description: Body length 1.40 mm, wing length 1.0 mm. HEAD: Wider than long; eyes large, bare, facets not differentiated. Ocellar triangle on small, slightly raised tubercle, with 2 long pairs of ocellar setae (setal lengths ca. same lengths as dorsocentral setae). 4–5 fronto-orbital setae very close to margin of eye. Antenna with flagellomere I setulose; arista situated dorsally; 3 aristal articles, basal two minute. Face with clypeus protuberant, pair of large, projecting setae. THORAX: Fairly broad, setose. Mesoscutum with row of acrostichal setulae; large pair of posterior dorsocentral setae, smaller dorsocentrals anteriad, several supra-alar and notopleural setae; scutellum with apical pair of long, cruciate setae, subapically with smaller pair (ca. 0.3x length of apicals). Legs long and slender; most distinctive feature is plumose hind tibia (probably a male character only), with 4 longitudinal rows of long, fine setae. Wing with vein C extended to apex of M1; Sc not observable; R1 meeting C at slightly less than basal third of wing; R2+3 curved upward toward C, distance between its apex and apex of R1 1/2 the length of cell r1; vein R4+5 forked with R4 and R5 widely divergent, length of fork slightly less than base of fork; M1 parallel to base of fork R 4+5; crossvein r-m slightly distal to bm-cu, separated by segment less than 1/3 length of either crossvein; vein M2 very diffuse, fold-like, incomplete at both ends; CuA1 tapered and incomplete apically; veins CuA2 + CuP not apparent, although anal lobe well developed. ABDOMEN: Slender, with male genitalia dorsoflexed. Male terminalia: Cerci fused, formed hood-like over phallus and surstyli; surstylus with two long lobes, dorsal one slender and digitiform, both lobes with apical setulae (vental lobe with 2–3 setulae on ventral margin). Phallus apically scoop-shaped; postgonite with apical setae, length approximately equal to that of ventral lobe of surstylus. Hypandrium large, convex. Female terminalia simple, apical segment a long and slender cone; cerci small.

Type. Holotype, male, LEBANON: “Ambre de Hammana/Mdeiru, Aptian inférieur, Collection Dany Azar, no. 230” on the label. Specimen is in a tiny (4 x 4 x 1 mm) clear yellow chip of amber, mounted in balsam on a microscope slide. The tiny chip includes the pyritized remains of two other complete Chimeromyia (both females) and the head of a fourth individual. In MNHP.

Etymology. From the Greek, pilos (hair), in reference to the hind tibia having a feathering of dense, long, fine setae.

Comments. The remains of four of these flies in such a minute piece of amber indicate they were either congregating at a resin flux or were swarming. Swarms in empidoids and other Diptera are usually comprised of males, into which females fly to become mated. The eyes of male Eremoneura that swarm are typically holoptic, but those of Chimeromyiidae are not.

This species appears to be one of the most primitive species of Chimeromyia, by plesiomorphically possessing a fairly well developed anal lobe at the base of the wing. In those empidoids that have crossveins bm-cu and r-m nearly contiguous (e.g., some extant tachydromiines), bm-cu is usually distal to r-m, unlike C.

pilitibia where bm-cu is slightly proximal to r-m. The primitive new genus Chimeromyina , however, shares the same configuration of crossveins with Chimeromyia.

Figures

FIGURE 5. Chimeromyia mediobscura, n. sp., Az 269 (MNHP), male. A. Right lateral habitus, showing setation of hind tibia and tarsus (B). This specimen shows visible abdominal muscle plaques.

FIGURE 6. Chimeromyia mediobscura, n. sp. A. Az 274 (MNHP), male, left habitus. For detail of terminalia see fig. 8 F. B. Az 649 (MNHP), male. For detail of terminalia see fig. 8 D, E. C. Az 440 (MNHP), right habitus. For detail of head and thorax see fig. 7 A.

FIGURE 7. Chimeromyia mediobscura, n. sp. in Lebanese amber. A. Az 440: left lateral view of thorax, fore femur, and head. B. Az 225: Detail of ventral surface of head, showing labrum. C. ibid., dorsal view of head and thorax.

FIGURE 8. Chimeromyia mediobscura, n. sp. A. Az 649, Wing. B, C. Legs, left metathoracic, mesal (B) and dorsal (C) views. D, E. Male terminalia, oblique dorsal (D) and oblique ventral (E) views. F. Az 274, male terminalia, left lateral view.

FIGURE 9. Chimeromyia pilitibia, n. sp., in Lebanese amber. A – C: Az 225 (MNHP), female. (for detail of genitalia, see Fig. 10 D). A. oblique dorsal habitus, with detail (B) of hind leg. C. Details of wing, showing venational features. D, E: Az 230 (MNHP), male, with pyritized remains of another individual in the background below. Details of hind tibia (E) show the long pilosity. For detail of genitalia see Fig. 10 B.

FIGURE 10. Chimeromyia pilitibia, n. sp., in Lebanese amber. A. Holotype male, Az 230 (MNHP), oblique dorsal habitus. B. Detail of terminalia of holotype, right lateral view (apex of terminalia point up). C. Mesothoracic femur (mesal surface), showing spination. D. Female terminalia, Az 225.