Endymiomyia quadra, 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 : 73-75

Endymiomyia quadra , new species

Figures 25 , 57

DIAGNOSIS: As for genus, by monotypy.

DESCRIPTION: Based on male. Body length 6.58 mm; thorax length 1.67 mm; head width 1.64 mm; wing length 6.52 mm; abdomen length 3.87 mm; abdomen width (at base) 0.48 mm. Dorsum of thorax and abdomen dark, color not discernable. Head (male): Large, broader than thorax, dorsoventrally slightly flattened. Eyes very large, holoptic for most of length of frons, bare; facets on frontal surface ca. 2× diameter of surrounding facets; presence/absence of median transverse line through eye not observable (eyes partially decayed); posterior margin of eye (preserved portion) not emarginate; frontal margins divergent above antennae and ventrad, very slight emargination around base of antenna; eye partially occupying ventral surface of head (gena). Ocelli small, ocellar triangle small, slightly raised; lateral ocelli touching inner margins of eyes. Antennae inserted near middle of front of head, antennal sockets nearly contiguous, touching inner margins of eyes. Clypeus very small, faintly convex; oral cavity not sunken above proboscis (only ventral to proboscis). Gena well developed, setose, with fine light setae; hypostomal bridge complete; postgena concave, posterior tentorial pits visible; shape of dorsal portion of occipital foramen not visible (e.g., constricted/bisected); occiput not fully visible but apparently not concave. Antenna: Stylate, with 4-articled flagellum; antenna held forward. Scape small, short, cylindrical; pedicel slightly larger, apex slightly expanded and with whorl of setulae; basal flagellomere drop shaped, apically tapered to narrow stem; flagellum articles 2, 3, and 4 forming slender stylus, articles 2 and 3 nearly equal in size, article 4 longer than 2+3; very fine, minute style at apex of antenna. Mouthparts: Short, tip of proboscis protruding slightly beyond frontal surface of head, labellum small (obscure). Palp very slender, digitiform, 2-segmented, segments approximately equal length, apical segment slightly expanded; both palpomeres with ventral brush of long, fine, light setae; palp setae nearly as long as palp. Palpal pit present, preapically on lateral surface. Labrum fine, narrow, tubelike, lateral margins almost/actually meeting ventrally; length of labrum equal to that of proboscis. Laciniae not visible. Labium short, setose, visible in ventral view. Thorax: Short, compact, dorsally somewhat flattened. Scutum and scutellum very dark, with sparse vestiture of very fine, golden setae, longest setae on posterior portion of scutum, margins of scutellum, laterally on thorax. Notopleural area with 3 stiff, black, bristlelike macrosetae just anterior to transverse suture; 1 slightly thinner such seta on supraalar area. Pleura largely obscured by fractures, but katepisternum large, deep, separating procoxae from mesocoxae. Katepisternum, anepimeron, meron bare. Proscutellum and postscutellum absent. Scutellum triangular in dorsal view. Wing: Very long, slender, significantly tapered apically. Vein C circumambient, but abruptly narrowed past apex of R 5; C thick, black on anterior edge; basicosta small, not deeply incised or lappetlike. Crossvein h long, sclerotized, slightly distal to level of arculus; crossvein sc-r present, very short. Sc long, complete, 0.64× length of wing. R veins thick, sclerotized (except R 4 and apex of R 2+3); R 1 parallel and very close to Sc, slender pterostigma surrounding apex; R 2+3 significantly tapered apicad into thin vein, preapically faintly sinuous, tip of R 2+3 reaches to 0.83× wing length. R 5 and Rs thick, virtually straight and in line. Base of R 4 forks nearly perpendicular from R 5, tip of R 4 upturned; tip of R 5 ending at wing tip. Cells br and bm of equal length. Crossvein r-m near base of cell d; cell d very long. M veins thin; M 2 slightly sinuous, short; short spur of M 3 present, attached to apex of cell d (occurs in both wings). CuA thick, sclerotized, CuP present as sclerotized, tubular vein, ending at level of cell bm apex. A 1 and CuA 1 fuse just before wing margin (cell cup closed). A 2 present, long, apically evanescent. Anal lobe and alula well developed; upper calypter small. Dorsal surface of wing base between stems of M+Cu and A 2 with small, crescentic bulla; smaller, rounded bulla at base of upper calypter. Halter knob broad, dark; stem light, slender, long. Legs: Long, slender, dark. Procoxa long, slender, well separated from meso- and metacoxae. Legs mostly preserved in unique specimen, but all except hind ones detached from body, jumbled; tips of hind tibiae lost. Tibial spurs 0-1-?. Metacoxal pegs present on anterior surface, well developed. Pretarsus with claws well developed, empodium setiform, stiff and bristlelike; pulvilli slender, crescent shaped, slightly longer than claws. Abdomen: In male, very slender, nearly cylindrical; tergites and sternites well developed, dark, lateral edges nearly meet. Tergite 1 very short, tergites 2–4 nearly equal in length (base of tergite 2 slightly swollen); tergite 9 small, triangular, lying at bases of gonocoxae. Tergites with long, fine, erect, light setae; setae longest and most dense on lateral surfaces of tergites 1–5, especially tergite 2 (setae here are longer than width of tergite). Terminalia (male): Tergite 8 short, transverse; tergite 9 small, triangular, lying between bases of gonocoxae. Gonocoxae large, broad, setose, scoop shaped (mesal surface concave); gonostylus small, subapical, lobate. Phallus very thin, long, stylate, lying in broader, flattened sheath; phallus longer than gonocoxa + gonostylus. Large setose lobe(s) (cerci?) ventral to phallus, with basal furrow into which phallus base lies; apex of lobe(s) pointed.

TYPE: Holotype, male, JZC Bu-209. The specimen is in a small cubic piece of amber trimmed from a larger cabochen-shaped piece that contains a cucujoid beetle, a small beetle of undetermined family, a psychodid midge, and a suspension of wood particles. The fly is virtually complete, except that the hind legs distal to the apices of the tibiae are lost at the surface, and although three other legs are preserved they are detached and lying near the body. Also, the ventral halves of the eyes have decayed away. Otherwise, the specimen is very well preserved, with venation fully exposed and much of the genitalia visible.

ETYMOLOGY: Latin for “square,” used as a noun in apposition, in reference to the 4-articled flagellum that is unique amongst Heterodactyla.

COMMENTS: By virtue of the setiform empodium and a process of elimination, this striking species is not a nemestrinid, acrocerid, or eremoneuran, but appears most consistent with Asiloidea . Another feature supporting this placement is the presence of bristlelike macrosetae on the thorax, which is a feature of Asiloidea + Eremoneura. Within Bombyliidae I have observed the presence of notopleural and supraalar macrosetae in Cyllenia, Henica , Nomalonia , Peringueyimyia , and some bombyliines, but not in more basal beeflies (e.g., phthriines, usiines). The macrosetae occur in the three genera of Bombyliidae described herein, as well as Endymiomyia . The fossil has very welldeveloped metacoxal pegs, which, albeit widespread in orthorraphans, occur among Asiloidea in Apsilocephalidae (including Burmapsilocephala , see below), Hilarimorpha (Hilarimorphidae) , the basal bombyliid genus Oligodranes , and the (rather phylogenetically intermediate) bombyliid subfamily Crocidiinae ( Yeates, 1994) . I am tentatively placing Endymiomyia in Bombyliidae , even though the flagellum has four articles. In all Heterodactyla ( Bombyliidae + Asiloidea + Eremoneura) the flagellum has three articles, so this is clearly plesiomorphic. Also, Endymiomyia lacks the depression/fossa on the dorsal wall of the oral cavity, which in all modern bombyliids (and the three Cretaceous genera above) extends up the face; this fossa accommodates the proboscis that projects forward in bombyliids. Endymiomyia has a vestigial spur of M 3, the vein of which is completely lost in all other bombyliids except for various genera and species in the derived subfamily Anthracinae .

Figures

FIG. 25. Endymiomyia quadra (stem-group Bombyliidae?), new genus and species, holotype JZC Bu-209. A. Wing, dorsal view. B. Detail of wing base, dorsal view. C. Detail of anterior portion of head, ventral view. D. Face, with antennae and mouthparts, oblique frontal view. E. Detail of antenna, lateral view. F. Male terminalia, dorsal view. Panels E, F to same scale.

FIG. 57. Endymiomyia quadra, new genus and species (stem-group Bombyliidae), holotype JZC Bu-209. A. Habitus, dorsal view. B. Head and thorax, dorsal view. C. Base of abdomen, showing long lateral pilosity. D. Male terminalia, dorsal.