Parachasmatonotus oesiensis, Published, 2007

Published, First, 2007, Chironomid midges from early Eocene amber of France (Diptera: Chironomidae), Zootaxa 1404, pp. 1-66 : 29-31

Parachasmatonotus oesiensis n. sp.

( Figs. 25 –26)

Etymology: This species is named after Oesia, the Latin name for the Oise River.

Diagnosis: Body ca. 3.2 mm long; 10 prealars; gonostylus apparently bare.

Description: Head 0.6 mm long, deformed; ocelli absent; antenna 1 mm long, much longer than head, distinctly hairy, with 11 flagellomeres covered with long setae (shortest 0.02 mm long, longest 0.43 mm long), pedicel broad and short, rounded, 11 th flagellomere 0.7 mm long; eye bare, without dorsomedial extension; mouthparts lacking functional mandibles; 5 palpomeres with setae; frontal setae absent, numerous postocular and inner and outer vertical setae. Thorax 0.98 mm long, 0.51 mm wide, 1.12 mm high; postnotum bare, with longitudinal median groove; surface of scutellum with numerous long setae in 2 rows; small scutal tubercle, high posterior gibbosity; acrostichals not visible,probably absent, dorsocentrals uniserial and biserial; scutum FIGURE 26. Parachasmatonotus oesiensis n. sp., holotype PA 685, drawing of male genitalia; a, ventral view; b, dorsal view (scale bar = 0.2 mm).

with median longitudinal groove; 10 prealar setae, no supraalar setae; epimeron II and preepisternum bare. Wing macropterous, 2.05 mm long, 0.37 mm wide, hyaline, membrane bare, but with coarse ponctation; anal vein An 2 absent; radius with 3 branches R 1, R 2+3 and R 4+5, R 2+3 not divided into R 2 and R 3; only M 1+2 and M 3+4 present; cross­vein MCu absent; squama fringed. Halter 0.3 mm long. Fore femur 1 mm long, tibia 1.14 mm long, tarsus 1.80 mm long; mid femur 0.8 mm long, tibia 0.92 mm long, tarsus 1.18 mm long; hind femur 0.97 mm long, tibia 1 mm long, tarsus 1.38 mm long; ta4 of all legs cylindrical, not cordiform; fore tibia with 1 long spur, mid and hind tibiae with 2 long spurs, hind tibial comb well developed; pulvilli present. Abdomen 2.15 mm long, 0.38 mm wide; gonostylus simple, elongate, hinged to gonocoxite and folded inward, seemingly bare; gonocoxite 0.16 mm long, 0.13 mm wide, with long setae apically and on outer surface, end of gonocoxite extending distal to articulation with gonostylus by 0.02 mm; anal point narrow and elongate, 0.13 mm long, 0.09 mm wide at base.

Discussion: Parachasmatonotus n. gen. is in the subfamily Orthocladiinae because of the following characters: macropterous, wings extending posterior to first abdominal segment; cross­vein MCu absent; tarsomere ta5 not trifid; gonostylus movable, folded inward; fore tarsomere ta1 shorter than fore tibia; and hind tibial comb consisting of free spiniform setae. In the key to the Holarctic orthocladiine genera of Cranston et al. (1989), Parachasmatonotus would fall near the extant genus Chasmatonotus Loew, 1864 , because of the following characters: wing well developed; R 1 and R 4+5 not forming thick clavus; eye without dorsomedial extension; pulvilli present; dorsocentrals uniserial and biserial; and scutum with median longitudinal groove (main character). This last character separates Chasmatonotus from all other Orthocladiinae . But Chasmatonotus differs from Parachasmatonotus by the following characters: male antenna short, plume reduced, with only five flagellomeres in Chasmatonotus , unlike 11 distinctly hairy flagellomeres in Parachasmatonotus ; palp (often) short; anepisternals sometimes present; preepisternals present; anal lobe strongly obtuse; squama without setae but sometimes up to five setae present; pseudospurs present on tarsomeres 1 and 2 of mid and hind legs; and anal point prominent, short and with short fine setae. All these characters are absent or different in Parachasmatonotus . For these reasons, we establish a new genus.

Material: Holotype PA 685, (male).