Pseudochasmatonotus furcatus, Published, 2007

Published, First, 2007, Chironomid midges from early Eocene amber of France (Diptera: Chironomidae), Zootaxa 1404, pp. 1-66 : 31-33

Pseudochasmatonotus furcatus n. sp.

( Figs. 27 –29)

Etymology: The name of this species refers to the forked gonostylus.

Diagnosis: As stated above for the genus.

Description: Head 0.32 mm long, deformed; ocelli absent; antenna 0.62 mm long, much longer than head, distinctly hairy, with 11 flagellomeres covered with long setae (shortest 0.01 mm long, longest 0.37 mm long), pedicel broad and short, rounded, 11th flagellomere 0.34 mm long, apex rounded, without subapical setae; eye bare, with strong parallel­sided dorsomedial extension, with 3 rows of ommatidia at minimum width; mouthparts lacking functional mandibles; postoculars absent, numerous frontals and inner and outer vertical setae.

FIGURE 28. Pseudochasmatonotus furcatus n. sp., holotype PA 2818, photograph of male genitalia.

FIGURE 29. Pseudochasmatonotus furcatus n. sp., holotype PA 2818, drawing of male genitalia (scale bar = 0.2 mm).

Thorax 0.5 mm long; postnotum bare, without longitudinal median groove; surface of scutellum with numerous long setae visible in 2 rows; scutal tubercle not visible; acrostichals absent, dorsocentrals biserial; scutum with median longitudinal groove; 3 prealar setae, 1 supraalar seta; epimeron II and preepisternum bare. Wing macropterous, 1 mm long, 0.28 mm wide, hyaline, membrane covered with numerous setae; anal vein An 2 absent; radius with 2 branches R 1 and R 4+5, R 2+3 seemingly absent; only M 1+2 and M 3+4 present; crossvein MCu absent; squama fringed. Halter 0.3 mm long. Fore femur 0.5 mm long, tibia 0.56 mm long, tarsus 1.22 mm long; mid femur 0.52 mm long, tibia 0.44 mm long, tarsus 0.6 mm long; hind femur 0.48 mm long, tibia 0.54 mm long, tarsus 0.82 mm long; ta4 of all legs cylindrical, not cordiform; fore tibia without long spur, mid and hind tibiae with 2 long spurs, hind tibial comb well developed. Abdomen 1.04 mm long, 0.12 mm wide; gonostylus 0.05 mm long, bifurcate, each narrow and elongate, respectively 0.02 mm long and 0.01 mm long, outer surface of 1 gonostylus covered with few setae; gonocoxite 0.11 mm long, 0.06 mm wide, with numerous long setae on outer surface; anal point not visible.

Discussion: The placement of this fossil in the Orthocladiinae is supported by the characters stated above. In the key to the Holarctic Orthocladiinae genera of Cranston et al. (1989), Pseudochasmatonotus n. gen. would fall near the recent genus Chasmatonotus because of the following characters: wing well developed; R 1 and R 4+5 not forming a thick clavus; scutum with a median longitudinal groove; and gonostylus bifurcate. However, Chasmatonotus differs from Pseudochasmatonotus in the following characters: male antenna short, plume reduced with only five flagellomeres; palp (often) short; eye without dorsomedial extension; anepisternals sometimes present; preepisternals present; anal lobe strongly obtuse; squama without setae but sometimes up to five setae present; and pseudospurs present on tarsomeres 1 and 2 of mid and hind legs. All these characters are absent or different in Pseudochasmatonotus . Furthermore, Parachasmatonotus differs from Pseudochasmatonotus by the following characters: eye without dorsomedial extension; 10 prealar setae unlike three prealars; wing membrane bare; and gonostylus simple. For these reasons we establish a new genus.

Material: Holotype PA 2818 (male).