Cretaenne rasnicyni Azar, Veltz & Nel, 2008

Lukashevich, Elena D. & Przhiboro, Andrey A., 2011, New Chironomidae (Diptera) with elongate proboscises from the Late Jurassic of Mongolia, ZooKeys 130, pp. 307-322 : 308-309

Cretaenne rasnicyni Azar, Veltz & Nel, 2008 sp. n.

Etymology.

Named in honour of an outstanding Russian palaeoentomologist Dr A.P. Rasnitsyn.

Material examined.

Holotype: part and counterpart of well-preserved female PIN 4270/2379 ±, SW Mongolia, Shar Teg (443/1); Late Jurassic. Paratypes: impressions of two females PIN 4270/2367 ±, 2459, from the same outcrop.

Diagnosis.

The new species is distinguished from both known species of Cretaenne by the longer proboscis (more than half of the head height and about twice the clypeus height) and the longer Rs stem.

Description.

Female. Measurements (mm): Total length 2.1-2.7 (holotype 2.3); thorax length ca. 0.8, width ca. 0.4; wing length 2.1-2.3 (holotype 2.1); abdomen length 1.35-1.8 (holotype 1.5). Total length / wing length 1.1.

Holotype

(Figs 1 a–d, 2 b–c). Coloration . Thorax dark, abdomen and legs lighter, at least some legs with slightly darker apices of femora and tibiae. Head ca. 550 μm wide, ca. 400 μm high to lower eye margin. Scape ca. 100 μm, pedicel ca. 30 μm in diameter. Clypeus ca. 200 μm wide, ca. 250 μm high. Proboscis with visible part ca. 350 μm long (possibly, without apex), tapering, sclerotized. Thorax. Postnotum wider than long, ca. 200 μm long, possibly with longitudinal median groove. Wing longer than abdomen, Sc clearly up to Rs level, thinning distally, possibly not reaching C (apical part of Sc not discernible). Vein C and radial veins strong, coloured (R2+3 thinner then others), as well as proximal sections of M and CuA, r-m and bM3+4. Long stem Rs subequal to r-m; R4+5 8-9 times as long as Rs; R2 distinctly longer than dR1. VR 1.1. Legs (lengths not measurable). Femora (mid- and hind) widened to apex, maximum 120 μm wide, with thin sclerotized ridge ventrally near apex. Tibiae (mid- and hind) apically 80-100 μm wide. Tarsi not preserved. Abdomen. Abdominal segments II–V: ca. 200 μm long, 500-600 μm wide. Three large subequal oval sclerotized spermathecae 140-150 μm long, ca. 100 μm wide, with necks (probably, short). Gonapophysis IX distinctly visible, sclerotized, with notum ca. 200 μm long, 15 μm wide at anterior end, with rami ca. 60 μm long. Probable gonocoxites VIII (gonacoxapodemes?) visible as moderately sclerotized small oval lobes near posterior end of notum. Cerci short, hardly visible.

Paratype.

(Figs 1 e–h, 2a). Visible characters as in holotype, with following additions. Head preserved only in PIN 4270/2367, 650 μm wide, 850 μm high with proboscis, ca. 400 μm high to lower eye margin. Eyes with medially narrowing dorsomedial extension, well separated by 60 μm. Coronal triangle ca. 130 μm high, ca. 100 μm wide; coronal suture clear, probably pair of poorly visible ocelli (ca. 30 μm in diameter) adjoining lower part ventrally to eye dorsomedial extension. Scape ca. 100 μm, pedicel ca. 40 μm in diameter. Flagellomeres (five distinctly visible lateral to eye margin) short-oval, 50-70 μm long, 30-40 μm wide. Clypeus ca. 200 μm wide, ca. 300 μm high. Proboscis ca. 550 μm long, sclerotized, stylet-like, pointed, with blade-like tapered laciniae and mandibles, labrum apically more sclerotized. Palpi poorly visible, looking widened (ca. 70 μm in distal parts); visible parts of palpi reaching about 4/5 of proboscis. Thorax. Scutum weakly, evenly convex; anterior part ca. 300 μm wide. Antepronotals narrowed medially. Scutellum ca. 120 μm long; postnotum ca. 200 μm long, 300 μm wide, with distinct longitudinal median groove. Legs. Measurements (μm). p1(?): ti 880, ta1-5 1200; p2: ti 1375, ta1 750-850, ta2 ca. 400, ta3-5 ca. 700, LR2 0.55; p3: fe 1000, ti 1450-1500, ta1-5> 1250. Tibiae 60-100 μm wide near apex. Apices of mid-, hind tibiae with combs of separate spiniform setae (visible only in PIN 4270/2459): midtibia with no less than 3-4 slenderer setae ca. 50 μm long, hind tibia with no less than 3 thicker setae, longest ca. 50 μm. Hind tibia probably with two spurs, 70 and 50 μm long.

Remarks.

The pattern of the female mouthparts is poorly visible in the holotype and unknown in paratype PIN 4270/2459; paratype PIN 4270/2367 has a well-preserved proboscis and its wing venation is very pale and incomplete; the setae at the tibial apices are distinctly visible only in paratype PIN 4270/2459; in both paratypes the spermathecae are not visible. Hence it is possible that these specimens are not conspecific. However, we suggest that all these specimens belong to the same species due to visible peculiarities of venation (particularly the long Rs stem and R2 position).

The genus Cretaenne was described in the subfamily Aenneinae with reservations, due to the vein Sc not terminating in the wing margin and short Rs stem, as distinct from the type genus of the subfamily, Aenne Ansorge, 1999 from the Late Triassic and Early Jurassic of Europe ( Krzeminski and Jarzembowski 1999, Azar et al. 2008). In the new species from Shar Teg, the stem Rs is long without doubt but Sc is clear only to the level of the first Rs bifurcation, then sharply thins out and possibly does not terminate in C, as seen in Cretaenne . We did not reexamine the type material of Aenne and Cretaenne , but according to the published data, Rs length can vary within species: in Aenne liasina Ansorge, 1999, the relatively long Rs is longer or shorter than r-m ( Ansorge 1999: figs 6-7), whereas the distal thinning of Sc is not recorded. Consequently, the new species is described here as a member of Cretaenne due to several features unknown for Aenne (described from isolated wings only), viz. a reduced hind tibial comb, the postnotum with a longitudinal groove, the structure of well-developed extended proboscis, and, probably, spurs on middle and hind tibia. Actually, biting mandibles were reported for the Mesozoic Aenne with reference to unpublished data of Cranston ( Grimaldi and Engel 2005: 504).