Jurassinemestrinus eurema, 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 : 55-59

Jurassinemestrinus eurema , new species

Figures 19 , 51

DIAGNOSIS: Very similar to J. orientalis Zhang based on the elongate br and bm cells, short stem of M 1+2, presence of a closed cell cup (with A 1 and CuA 2 meeting just before wing margin). J. eurema , however, has: R 2+3 much more sinuous (as in Sinomusca ), cell br much thicker, and the stem of R 4+5 much more arched. It differs from J. orientalis and Sinomusca mostovksii most distinctively by the presence of an r-r crossvein (between the apices of R 2+3 and R 4) and an r-m crossvein (between the stem of R 4+5 and base of M 1), thus forming two subapical cells. These two crossveins are considered minor (species-level) modifications, often seen in orthorrhaphans as a bracing mechanism for the wing tip during flight.

DESCRIPTION: Based on male. Large fly, 8.88 mm body length; thorax length 3.01 mm; abdomen length 4.50 mm; wing length 7.09 mm. Head: Very large, length 1.9 mm; hemispherical, pipunculidlike (especially in lateral view); depth of head slightly greater than that of thorax. Eyes occupy virtually all of head, dorsally, frontally, ventrally. Cheeks and parafacial plates not present, these spaces occupied by eyes. Eyes holoptic for 0.85× length of frons; fully bare, no pilosity; no differentiation (e.g., dorsoventral) of facets. Posterior margin of eyes with small, V-shaped emargination connected to fine line dividing dorsal and ventral halves of eye; line extends to about middle of eye. Frontal margins of eyes (between antenna and proboscis) separated by very narrow width equal to diameter of facets. Ocelli well developed, in very narrow triangle between eye margins, width ca. 5× eye facet diameter; posterior ocelli facing opposite (laterad), anterior ocellus facing anteriad; very narrow longitudinal ridge posterior to ocelli. Occiput dark, without pilosity; deeply and virtually entirely concave. Antenna: Very small, length 0.7 mm. Scape barely exposed, pedicel scoop shaped (ventral margin longer), flagellomere 1 largest article, oblong, slightly longer than apical article; apical article stylate, digitiform, apex blunt, with minute microtrichia and without minute apical stylus. Mouthparts: Small; slightly exposed beyond margins of eyes; labellum well developed, laterally very compressed. Palps present, laterally compressed, segmentation obscure. Clypeus very small, slightly exposed above labellum. Thorax: Robust, devoid of long pilosity, dorsally with minute setae, no macrosetae; cuticle color appears to be dark yellow to orange. Transverse scutal suture absent. Anterior spiracle large, slitlike, ver- tical; posterior spiracle surrounded by membrane. Anepisternum, anepimeron, katepisternum well defined. Scutellum in dorsal view a narrow triangle, apex very narrow and laterally compressed. No pre- or postscutellum present. Bases of procoxae far anterior to mesocoxae; meso- and metacoxae nearly in contact. Wing: Long and fairly narrow; anterior and posterior edges nearly parallel. Wing hyaline, except for heavily sclerotized pterostigma between apices of Sc and R 1; edges of pterostigma discrete. Wing membrane glassy, devoid of microtrichia; with coarse, shallow, irregular furrows (not fine, parallel pleating). Sc and R 1 long, apex of latter reaching to 0.8× length of wing. R 1 slightly sinuous. R 2+3 very sinuous; apical portions of R 2+3, R 4, R 5, M 1, M 2, and M 3 very short. Uniquely with r-r crossvein (between the apices of R 2+3 and R 4) and r-m crossvein (between stem of R 4+5 and base of M 1), thus forming two subapical cells (rr, rm); base of R 4+5 stem with short, incomplete vein projecting into cell rr (this vein shorter in right wing). Cell br same length as cell bm, bm much thicker. Cell dm an irregular hexagon. Cell cup closed (CuA 2 and A 1 meet shortly before wing margin), CuA 2 short, slightly sinuous; A 2 present as short vein apically evanescent into anal region. Anal lobe very small, alula well developed, upper calypter present but small, lower calypter absent. Tegula well developed. Halter with narrow stem, knob darker. Legs: Slender, without macrosetae, with dense vestiture of fine microsetae on tibiae and tarsi. No tibial spurs. Tarsi and apices of tibiae darker than rest of legs. Procoxae long, adpressed to sternum, medial margins mostly in contact; meso- and metacoxa small; metacoxa without knob on anterior surface. Femur length longer than that of respective tibia. Pro- and mesobasitarsomeres short, lengths of each about equal to that of respective tarsomeres 2+3+4; metabasitarsomere length equal to combined length of metatarsomeres 2–5. All tarsomeres 2–4 funnel shaped, with apical ring of setulae; apical tarsomere large, broad, length equal to combined length of tarsomeres 2–4. Pretarsal structures large; claws large, simple; empodium pulvilliform, larger than pulvilli; all lobes slightly longer than 1 with pair of paramedian lobes, forming depresclaws. Abdomen: Relatively large, broad, dorso- sion/groove for reception of narrow scutellar ventrally flattened. Width greater than width of apex. Posterior margins of tergites 2–4 raised, head or thorax. Tergites and sternites all wide, forming slight transverse mounds (best seen in lateral margins in contact (pleural membrane not lateral view). Sternite 7 small, triangular. Male exposed or very small, or both); without pilosity Terminalia: Small, projected posteriad, well or macrosetae, with minute, stiff setulae. Tergite exposed. Epandrium a small, flat, unspecialized tergite; cerci 1-segmented, setose, laterally compressed, ventral margin flat; aedeagus exposed terminally beneath cerci, apex pointed, not extending beyond apex of cerci; gonostylus well developed, sclerotized, base broad, apex curled mediad with tip pointed; gonocoxa a simple setose lobe at base of gonostylus, overlapping its base. Female Terminalia: Unknown.

TYPE: Holotype, Male AMNH Bu-SE3/3.

ETYMOLOGY: From the Greek, eurema (a noun in apposition), “that which is found unexpectedly.”In reference to the revealing nature provided by this species on the relationships of Rhagionemestriidae .

COMMENTS: The type and unique specimen is superbly preserved and entirely complete in a light yellow, almost fully transparent (slightly turbid) prism-shaped piece of amber, 22 mm length × 8–10 mm on each side.

Figures

FIG. 19. Jurassinemestrinus eurema (Rhagionemestriidae), new species, holotype AMNH Bu-SE3/3. A. Wing. B. Head, right lateral view. C. Antenna, lateral view. D. Left protarsus, ventral view. E. Posterior portion of thorax and anterior portion of abdomen, oblique dorsal view, showing shapes of scutellum and groove on tergite 1. F. Male terminalia, oblique right lateral view. Panels C, D to same scale.

FIG. 51. Jurassinemestrinus eurema, new species (Rhagionemestriidae), holotype AMNH Bu-SE3/3. A. Habitus, right lateral. B. Head and thorax, right lateral. C. Habitus, ventral. D. Head, ventral. E. Right wing. F. Tarsi. G. Male terminalia.