Lindneromyia neomedialis Grimaldi 2018, new species

Lindneromyia neomedialis, new species Figures 9, 34

DIAGNOSIS: (male only). Vein M unforked (M 2 lost), R 4+5 and M 1 slightly sinuous; gena completely and occiput virtually bare; metatarsomeres 1–4 flattened, expanded, basitarsomeres short, tarsomere 3 longest; acrostichals completely absent; only 1 (short) pair dorsocentrals and scutellars present; 2 notopleurals; wing membrane with very faint, minute microtrichia over about half of wing (mostly posteriorly); male abdominal segments 7–8 inserted into deep emargination of posterior portion of tergite 6.

DESCRIPTION: (male only). Head: Large, broader than thorax. Eyes bare, large, occupying all of lateral portion and much of frontal surface of head; holoptic in male from just above antennae to anterior ocellus (~15 facets); dorsal facets about 2× diameter of ventral ones. Median furrow of frons, interfrontal setae, orbitals, verticals (presence/absence) not observable. Ocelli on tubercle; setae absent, 6 minute setulae present. Postocular setae minute, in short row along posterodorsal margin of eye; occiput otherwise bare. Vibrissa, genal setae absent. Antenna: Slight oval depression on face beneath each antenna. Scape small, bare; pedicel cup shaped, with 4–5 setulae on rim; arista terminal; basal flagellomere short, roughly drop shaped but without slender apical extension. Arista with two minute, ringlike articles at base; basal aristomere long, fine, bare (not micropubescent). Mouthparts: Oral margin and clypeus squared; clypeus thin. Palp small, with apex truncate (possibly with a pore). Labellum (opened) broad, with ~10 pseudotracheae; labrum not observable.

Thorax: Scutum rounded but not arched; curvature greater on anterior portion; scutum and scutellum appear black, perhaps velvety. Acrostichals absent; only one pair of (short, prescutellar, inclinate) dorsocentrals present (smaller graded dcs completely absent). Supraalar setae absent; 1 short postalar; 2 short notopleurals; anepisternum and katepisternum bare. Prescutellum absent. Scutellum with only one pair of small preapical setae, divergent. Wing: Length/width 2.0, hyaline except for faint tint between Sc and R 1. Membrane with faint, minute, barely detectable microtrichia over about half the (posterior portion of) wing, including much of cell Sc. No veins with setulae or spinules; prehumeral costal seta very small; vein C with spinules to slightly past apex of R 2+3; C terminates at apex of M 1. Sc relatively short, close to R 1; pterostigma absent. R 2+3 almost straight, R 4+5 and M 1 slightly sinuous, convergent at wing tip; R 4+5 ends near wing tip; cells br, bm closed. Crossvein dm-cu short, distant from wing margin, 5× its length from wing margin (vs. ca. 0.5–3×). M unforked (M 2 lost), without abrupt bend in M 1. CuA 1 relatively straight; cell cup pointed, CuP straight (not curved); anal lobe and alula well developed. Halter knob large, dark, bulbous, length ~ equal to that of stem.

Legs: Relatively short; all femora without macrosetae, spines or tubercles. Tarsomeres 1–4 flattened, expanded; tarsomere 3 longest, 1 is broadest. All tarsomeres with posteroventral, seamlike row of dark, bifid scales; more such scales scattered over dorsum of metatarsomeres; 2 sparse rows of scales dorsally on meso- and metatibia. Mesotibia with single, short ventroapical spur, length less than diameter of tibial apex. Pulvilli well developed; empodium setiform.

Abdomen: Dark; relatively short, as preserved only slightly longer than thorax. Tergites well developed, wrap laterally, contact lateral margins of sternites (which are also well developed). Abdomen laterally with fine, erect setae; dorsally with few or no setae (probably velvety black); terminal tergites without large, spinelike setae. Six tergites visible dorsally, 2 small ones ventrally (tergites 7 and 8) (plus epandrium), all three ventroflexed (presumably completely circumverted), recessed in deep emargination on posterior portion of tergite 6. Cerci light, appear fused at bases. Posterior margin tergite 6 without thick, stiff setae; epandrium crescentic.

SPECIMENS EXAMINED: Holotype, male, AMNH DR14-35, from mines near Santiago, Dominican Republic (Miocene). Specimen is complete and has excellent preservation, although the surface of the amber is crazed.

ETYMOLOGY: Neo -, referring to New World; and - medialis, referring to the medial vein, as this is the only New World species of the genus thus far with a simple medial vein.

COMMENTS: Lindneromyia is the largest genus of the family, and the predominant one in the tropics. Three species in the genus have a simple medial vein: L. africana Kessel (from Kenya, type species of the genus), L. fonsecai Chandler (from Australia), and L. kesseli Bowden (from South Africa). Lindneromyia neomedialis significantly differs from these three species based on the single pair of dorsocentrals (vs. in two rows) and scutellars (vs. 2–3 pairs); lack of stiff setae on tergite 6 (which is widespread in Platypezidae); and the very distinctive, short dm-cu crossvein distant from the wing margin (vs. very close to the margin). Lindneromyia fonsecai has a very abrupt bend in M 1 (some individuals retain a spur of M 2). Lindneromyia africana is reported to lack the small basal aristomeres (which would be very unusual, perhaps an observational error), and the basal flagellomere is setose (not just with microtrichia); dm-cu is extremely close to the wing margin (~ 0.3× crossvein length), and R 1 is quite long (terminating at level of CuA 1 apex). Despite these differences I am hesitant to accord a separate generic status to the fossil, especially since the external male terminalia agree so closely with Lindneromyia (e.g., Chandler, 1994; Chandler, 2001). Also, many of the distinctive features of L. neomedialis are autapomorphic losses.

Lindneromyia neomedialis differs from Metaclythia (monotypic: currani Kessel, known from Ontario, Canada, and Wisconsin, United States), which also has a simple M vein, based on the following: Cell dm short (vs. long), gena bare (vs. setose); single pair of dorsocentrals (vs. in graded row); scutellars in single pair (vs. two); 2 (vs. 4) notopleurals; tergite 6 lacking spinelike setae (vs. with 2 pairs).