Corynoneura eocenica, Published, 2007

Published, First, 2007, Chironomid midges from early Eocene amber of France (Diptera: Chironomidae), Zootaxa 1404, pp. 1-66 : 22-25

Corynoneura eocenica n. sp.

( Figs. 19 –21)

Etymology: This species is named after the Eocene period.

Diagnosis: Antennae with 11 flagellomeres; 4 setae on apical antennal segment forming rosette, with plume hairs basally; eyes bare; radius froming thick clavus, before midpoint of wing and well basal of Cu 1; weak ‘false’ vein continuing from RM; surface of scutellum with 4 long setae; scutal tubercle probably absent; dorsocentrals uniserial and decumbent; keel only on fore trochanter; hind tibia broadened at apex; gonostylus hinged to gonocoxite and folded inward, short, with apical megasetae but no crista dorsalis.

Description: Male head deformed, 0.22 mm long; ocelli absent; antenna 0.41 mm long, much longer than head, distinctly hairy, with 11 flagellomeres covered with long setae (shortest 0.008 mm long, longest 0.20 mm long), pedicel broad and short, rounded, 11th flagellomere much longer, rounded apically, 0.1 mm long, four setae on apical antenna forming one rosette, with carries plume hairs basally on terminal segment; eyes bare, with small dorsomedial extension, with 3 or fewer rows of ommatidia at minimum width; mouthparts lacking functional mandibles; 5 palpomeres with numerous setae, but p3 with 2 distinctly longer apical setae; clypeus with few dorsal setae; postocular, frontal, inner vertical and outer vertical setae not visible, maybe absent. Thorax 0.43 mm long, much longer than 0.12 mm wide, 0.3 mm high; postnotum bare, with visible longitudinal median groove; surface of scutellum with 4 long setae; scutal tubercle not visible, probably absent; acrostichals and dorsocentrals uniserial and decumbent; scutum without median longitudinal groove; epimeron II, posterior mesanepisternum II, and dorsal antepronotum bare; anapleural suture distinct. Wing macropterous, 0.71 mm long, 0.23 mm wide, hyaline, membrane bare; anal vein An 2 absent; radius forming thick clavus, before midpoint of wing and well basal of Cu 1; weak ‘false’ vein continuing from RM, closely parallel to costal margin, distally vanishing in wing membrane slightly basal to level of apex of M; M 1+2 and M 3+4 present; cross­vein MCu absent, anal lobe not developed. Halter 0.13 mm long. Fore femur 0.22 mm long, tibia 0.21 mm long, tarsus 0.37 mm long; mid femur 0.30 mm long, tibia 0.28 mm long, tarsus 0.35 mm long; hind femur 0.27 mm long, tibia 0.27 mm long, tarsus 0.38 mm long; strong keel on fore trochanter but not on other legs (clearly visible in PA 7074, less visible in other specimens); 4 th tarsomeres of all legs cordiform and shorter than tarsomere 5; presence of well­developed hind tibial comb; hind tibia broadened at apex, broadest part 2 times as broad as narrowest part. Abdomen 0.5 mm long, 0.12 mm wide, with few long setae on mid line of tergites; gonostylus narrow and elongate, 0.04 mm long, 0.008 mm wide, hinged to gonocoxite and folded inward, with apical megasetae but no crista dorsalis; gonocoxite 0.07 mm long, 0.01 mm wide, with long setae; anal point weak, if present.

3+4

Female head deformed; ocelli absent; antenna 0.13 mm long, shorter than head, with few setae, with 5 flagellomeres, pedicel narrow and short, rounded, 5 th flagellomere much longer than other flagellomeres, 0.06 mm long, numerous short setae on half of terminal segment, without setae basally; eyes bare, without dorsomedian extension; mouthparts lacking functional mandibles; 5 palpomeres; clypeus with few dorsal setae; with 2 postocular setae, frontal and inner vertical and outer vertical setae not visible, maybe absent. Thorax 0.4 mm long, 0.16 mm wide, 0.25 mm high; postnotum bare, with longitudinal median groove; surface of scutellum with 4 long setae; scutal tubercle not visible, probably absent; acrostichals uniserial and decumbent, dorsocentral setae not visible; scutum without median longitudinal groove. Wing macropterous, 0.68 mm long, 0.26 mm wide, hyaline, membrane bare; anal vein An 2 absent; radius forming thick clavus, before midpoint of wing and well basal of Cu 1; weak ‘false’ vein continuing from RM, closely parallel to costal margin, distally vanishing in wing membrane slightly basal to level of apex of M 3+4; M 1+2 and M 3+4 present; cross­vein MCu absent, anal lobe not developed. Halter 0.09 mm long. Fore femur 0.23 mm long, tibia 0.19 mm long; mid femur 0.22 mm long, tibia 0.2 mm long, tarsus 0.25 mm long; tibia 0.25 mm long, much than tarsus 0.23 mm long; strong keel on fore trochanter but not on other legs (not visible in this specimen); 4th tarsomeres of all legs cordiform and shorter than tarsomere 5; presence of well­developed hind tibial comb; hind tibia broadened at apex, broadest part 2 times as broad as narrowest part. Abdomen 0.31 mm long, 0.20 mm wide.

Discussion: In the key to dipteran families of McAlpine (1981), our specimens fall in the family Chironomidae . In the Nearctic keys to genera of Oliver (1981) and to the key to Holarctic subfamilies of Oliver & Dillon (1989) and to Palaearctic subfamilies in Saether et al. (2000), they fall in the subfamily Orthocladiinae because of the following characters: macropterous, wing 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. They are in the genus group { Corynoneura Winnertz, 1846 , Thienemaniella Kieffer, 1909, Onconeura Andersen & Saether, 2005 , Physoneura Ferrington & Saether, 1995 , Tempisquitoneura Epler & de la Rosa, 1995 , Ichthyocladius Fittkau, 1974 , Notocladius Harrison, 1997 } because of the following characters: presence of a thick clavus before midpoint of wing and of a ‘false vein’, and all tarsomeres ta4 cordiform and shorter than ta5 ( Mendes et al. 2004, Andersen & Saether 2005). The exact nature of the clavus and ‘false vein’ remains controversial ( Saether & Kristoffersen 1996).

FIGURE 20. Corynoneura eocenica n. sp., holotype PA 15003, drawing of general habitus (scale bar = 0.5 mm). FIGURE 21. Corynoneura eocenica n. sp., paratype PA 7074, drawing of fore trochanter (Tr) (scale bar = 0.1 mm).

The thickened clavus distinctly basal to Cu 1 of our fossils excludes affinities with Physoneura ( Ferrington & Saether, 1995) . The absence of a trochanter keel on the mid and hind legs, the hind tibia apex broadened, and the ta4 cordiform exclude affinities with Onconeura ( Andersen & Saether 2005) . The reduced or absent scutal tubercle, the presence of a well­developed hind tibial comb, and the cordiform ta4 of our fossils exclude affinities with Ichthyocladius ( Mendes et al. 2004) . The reduced anal lobe of our fossils excludes affinities with Tempisquitoneura ( Epler & de la Rosa 1995) . Thienemaniella and Corynoneura are more difficult to separate. Notocladius and Thienemaniella have eyes hairy or pubescent, unlike our fossils ( Harrison 1997). The decumbent dorsocentrals and apically broadened hind tibia suggest affinities with Corynoneura , but the ‘false vein’ ending proximal to the apex of M 3+4 would support affinities with Thienemaniella ( Mendes et al. 2004). The presence of a dorsal keel on the fore trochanter is considered a possible character to separate these two genera (Cranston et al. 1989), but Mendes et al. (2004) indicated that this character is polymorphic in Thienemaniella. We tentatively attribute our fossil specimens to Corynoneura .

In the key to the Chironomidae of Africa by Freeman (1956), the fauna of Australia by Freeman (1961), and world revision of Hirvenoja & Hirvenoja (1988), our fossils would fall near Corynoneura dewulfi Goetghebuer, 1935 , or C. australiensis Freeman, 1961 , because of the following characters: presence of a rosette of short hairs on apical antennal segment ( Freeman 1955: fig. 16d) and rosette hairs less than half the length of the terminal segment, with plume hairs basally. However, there are only four setae forming this rosette in our fossil, and the presence of long setae on the outer surface of each gonocoxite excludes these affinities.

Both Corynoneura and Thienemaniella are widespread and their larvae live in permanent water bodies. Because the ‘ Corynoneura ’ group of genera is unknown in the fossil record, we recognize a new species for these fossils.

Material: Holotype PA 15003 (male). Male paratypes PA 7074, PA 12385, PA 6218, PA 10809, PA 7275, PA 10128, PA 10928, PA 8355, PA 10928, PA 7740, C97169 (H. Henrotay), PA 15004, PA 1437, PA 215, PA1636, PA 2744, PA 10672, PA 10681, PA3652, PA 7882, PA 1657, PA 20 (2/2), PA 5182, PA 5720, PA 8139, PA 5767, PA 8144, PA 2975 (3, 4, 5/5), PA 12233, PA 1333, PA 6118, PA 5582, PA 4388, PA 5556, PA 2393 (7/9), PA 2796 (1, 2, 3/4), PA 6573, PA 6559, PA 28, PA 833, PA 1053, PA 941, PA 826, PA 602 (2/2), PA 647, PA 473, PA 899, PA 5440, PA 359 (5/6), PA 1845, PA 1851, PA 9358, PA 9029, PA 9422, PA 9086, PA 5314, PA 1466, PA 6805, PA 15028, PA 15037, PA 2947, PA 3616, PA 6871, PA 5147, PA 8154, PA 168(1,2/4), PA 4984, PA 3442, PA 3954, PA 3895, PA 3933, PA 1927, PA 5896, PA 6566, PA 532, PA5277, PA 2487, PA 2518, PA 2476 (2/2), PA 6541, PA 2960, PA 7527, PA 8286, PA 8389, PA 9954, PA 15011, PA 2908, PA 3393, PA 2211, PA 6592, PA 408 (1,2,3,4/4), and PA 7480. Female paratypes PA 6218, PA 15004, PA 70 (3/3), PA 359 (2,3/6), PA 10395, PA 1693, PA 3370, PA 4957, PA 3426, PA 42 (1/2), PA 5148, PA 415, PA 5355, PA 5720, PA 8139, PA 2827 (6/6), PA 1258, PA 6198, PA 3993, PA 3909, PA 3609, PA 6573, PA 951, PA 636, PA 5427, PA 1851, PA 9029, PA 12395, PA 6783, PA 15024, PA 4984, PA 3442, PA 730, PA 429 (1/5), PA 653, PA 418, PA7595, PA 5173, PA 5384, PA 12303, PA 1314, PA 1215, PA 5096, C 97162, PA 6592, PA 2954, PA 7828, PA 8839, PA 8286, PA 8155, PA 8182, PA 10743, PA 2908, PA 3926, PA 3653, PA 5579, PA 1785, PA 4432, PA 3490, PA 3176, and PA 6544.