Flagellomere 12 with apical process, setulose in both sexes; tarsal claws simple and curved beyond basal third; male cerci secondarily lobed; gonostyli 8–9 times as long as wide; aedeagus elongate, tapering to the apex and constricted subapically; pupa with antennal basis well projected, cervical sclerite bilobed at the middle of the superior margin, abdominal dorsal spines absent, larva with spatula with long stalk and four pairs of setose terminal papillae.

Holotype male. Brazil, Minas Gerais State: Quartel São João municipality, III.2009, L. Oliveira leg. Paratypes, same locality, data and collector: 3 males, 9 females, 7 pupal exuviae and 15 larvae. All deposited in MNRJ.

Fusiform and cylindrical body; 2.60–3.85 mm long (n = 11). Integument rough. Spatula (Fig. 1): 0.22–0.35 mm long (n = 11), two-toothed, apical teeth triangular with rounded apex, stalk narrow, except basally, very long, about 6.5 times as long as anterior part of spatula. Two groups of three lateral papillae on each side of spatula (one pair setose in each group) (Fig. 1). Terminal segment (Fig. 2) with four pairs of terminal papillae: one pair with setae as long as dorsal setae of eight abdominal segment, one pair with setae about half as long, two pairs with short setae.

Body length: 3.25–3.95 mm (n = 6). Head (Fig. 3): cervical sclerite bilobed at the middle of the superior margin, apical setae 0.10–0.13 mm long (n = 10); antennal basis with superior margin pronounced in a conspicuous horn-like process; two pairs of lower facial papillae, one pair with seta and another lacking setae, three pairs of lateral facial papillae, one pair with seta and two lacking setae. Prothoracic spiracle (Fig. 3) elongate 0.18–0.26 mm long (n = 9), digitiform. Abdominal segments 2–8 without conspicuous spines.

Body length: 2.90–3.40 mm in male (n = 3), 3.40–4.30 mm in female (n = 9). Head (Fig. 4): occipital process present. Eye facets hexagonal, all closely approximated. Antenna: scape subcylindrical, pedicel spheroid, both with few setae and scarce scales, male flagellomeres binodal and tricircumfilar, nodes setulose and necks bare; circumfila loops regular in length (Fig. 5); male flagellomere 5: 0.15–0.18 mm long (n = 4), basal node 4.1–5.8 times shorter than the total length of the flagellomere, basal neck 5.3–8.6 times shorter than the total length of the flagellomere, distal node 2.5–3.0 times shorter than the total length of the flagellomere, and distal neck 3.2–3.6 times shorter than the total length of the flagellomere; female flagellomeres cylindrical, node setulose and neck bare; flagellomere 5: 0.18–0.20 mm long (n = 8), node 2.7–3.3 times shorter than the total length of the flagellomere, circumfila as two connected horizontal rings (Fig. 6). Flagellomere 12 with apical process, setulose in both sexes. Frontoclypeus with 6–8 setae in male (n = 4), 6–10 in female (n = 5). Labrum triangular, long-attenuate, with 3 pairs of ventral sensory setae. Hypopharynx shorter than labrum, with anteriorly directed lateral setulae. Labella 0.07–0.09 mm long (n = 9), elongate-convex, each with long lateral setae and three pairs of short mesal sensory setae. Palpus 0.18–0.28 mm long in male (n = 4), 0.28–0.34mm in female (n = 6) with four crescent cylindrical segments, all with setae.

Thorax. Wings: length: 2.15–2.55 mm in male (n = 5), 3.05–3.35 mm in female (n = 8); venation: R1 2.22–3.04 times shorter than wing length, Rs evanescent, R5 curved, joining C beyond wing apex, M3 evanescent; CuA forked. Scutum with 4 longitudinal rows of setae with a few scales intermixed, the 2 dorsocentral rows broadest anteriorly and as single row on posterior half of sclerite, the 2 lateral rows in double row continuous along length of scutum. Scutellum with abundant setae, absent mesally. Anepisternum with a few scales dorsally; anepimeron with 7–14 setae (n = 5); other pleura bare. Tarsal claws simple, bent beyond midlength, gradually attenuate to apex; empodium short, not reaching bent in claws (Fig. 7).

Male abdomen (Fig. 8): tergites 1–7 rectangular with distal row of setae, setae irregularly distributed at midlength and laterally, anterior pair of trichoid sensilla, and mostly covered elsewhere with scales; eight tergite narrow, sclerotized with only anterior pair of trichoid sensilla as vestiture. Sternites 2–8 rectangular, with distal row of setae, setae irregularly distributed at midlength and laterally, anterior pair of trichoid sensilla, and mostly covered elsewhere with scales. Trichoid sensilla of sternites more closely approximated than those of tergites. Mesal and lateral setae of sternites more numerous than those of tergites.

Male terminalia (Fig. 9): gonocoxite 0.23–0.25 mm long and 0.09–0.10 mm wide, 1.90–2.50 as long as wide, 1.15–1.35 times longer than gonostylus (n = 4), cylindrical, with triangular mesal lobe; gonostylus 0.18–0.20 mm long and 0.02–0.03 mm wide, 8–9x as long as wide (n = 4), elongate, slightly constricted at midlength, striate at distal 2/3 and setulose at basal 1/3; cercus setose and secondarily lobed, inner lobe longer than outer lobe; hypoproct deeply concave apically, each resulting lobe widely separated from each other and with two apical setae; aedeagus elongate, tapering from basis to apex, constricted subapically, with rounded apically.

Female abdomen (Fig. 10): tergites and sternites 1–7 rectangular as in male; eight tergite not sclerotized, with only anterior pair of trichoid sensilla as vestiture.

Ovipositor barely protrusible, female cerci (Fig. 11) elongate-ovoid and setose, with apical pair of seta stronger than the others, hypoproct narrow, elongate with two apical setae.

(Fig. 12). On abaxial leaf surface, isolated or in groups near the veins, pear-shaped, with a basal peduncle and an apical reddish spine-like projection, green, glabrous, one-chambered, occupied by a single larva and with rigid wall.

The name quartelensis refers to the locality where the specimens from the new species were collected.

Clinodiplosis includes adults with simple or toothed tarsal claws, curved at their basal third or beyond midlength. The new species has simple claws, curved beyond midlength. Only five Neotropical species exhibit simultaneously both characters, i.e.: C. alternantherae Gagné, 2004, C. bellum Urso-Guimarães & Carmo-Neto, 2015, C. cattleyae Molliard, 1903, C. conica Oliveira & Maia, 2008 and C. eupatorii (Felt, 1911).

Among those five species, only C. bellum and C. quartelensis have the male cercus secondarily lobed. Other resemblances between these species are: the setulose apical process in the 12th female flagellomere; the deeply bilobed male hypoproct with convergent lobes; the elongate, tapering to the apex and constricted subapically aedeagus; the obtuse mesobasal lobe of the gonocoxites; pupa lacking dorsal spines on abdominal segments; and larva with no corniform papillae. Adults of both species can be distinguished by the length and proportions among the segments of the palpus (longer with crescent segments in C. quartelensis sp. nov.), wing venation (presence of M₄ only in C. quartelensis sp. nov.), and level of sclerotization of male 8th tergite (sclerotized only in the new species). Furthermore, the pupa of C. quartelensis sp. nov. differs from that of C. bellum mainly by the superior margin at the middle of cephalic dorsal plate narrow bilobed (wide with the entire superior margin at the middle in C. bellum). In addition the spatula is missing in C. bellum.

The host plant, Banisteriopsis membranifolia, is an endemic plant in Brazil. Considering that 92% of the Brazilian fauna of Cecidomyiidae are monophagous (Carneiro et al. 2009), the new galling species probably is endemic too.