Libanodiamesa deploegi, Veltz & Azar & Nel, 2007

Veltz, Isabelle, Azar, Dany & Nel, André, 2007, New chironomid flies in Early Cretaceous Lebanese amber (Diptera: Chironomidae), African Invertebrates 48 (1), pp. 169-191 : 184-186

Libanodiamesa deploegi sp. n.

Figs 15–17

Etymology: After Mr Gaël De Ploeg who with great talent, helped in preparing the material for study.

Description: Head 0.26 mm long. Ocelli absent. Antenna 0.5 mm long, almost twice as long as head, distinctly hairy, with 13 flagellomeres, all covered with long setae (shortest 0.04 mm, longest 0.18 mm). Scape broad and short, rounded; pedicel very short. Eye bare, with distinct dorso-medial extension. Mouthparts lacking functional mandible; palps long, with four visible palpomeres bearing numerous setae, last palpomere the narrowest and longest. Two postocular setae; frontal, inner vertical and outer vertical setae not visible, possibly absent.

Thorax 0.8 mm long, 0.6 mm wide, 0.8 mm high. Postnotum, scutellum, scutum without visible setae.

Wing macropterous, 1.2 mm long, 0.41 mm wide, hyaline; membrane without setae. Costa ending at apex of R 4+5; radius with only 3 branches R 1, R 2+3, and R 4+5; R 1 rather long, 1.66 times as long as R 4+5; R 2+3 simple, closely aligned and parallel to R 1. Crossvein MCu present, in a very basal position, about midway between base of M and RM. Fork of Cu nearly opposite RM; Cu 1 curved. Anal vein An 2 absent. Halter 0.14 mm long.

Fore femur length 0.46 mm, mid femur 0.5 mm, hind femur 0.44 mm.

Abdomen narrow, 0.2 mm wide.

Holotype: specimen 66, all tibiae apically broken, tibial spurs destroyed, tarsi missing, apex of abdomen destroyed. LEBANON: Mont Lebanon district [Mouhafazit Jabal Loubnan]: Hammana / Mdeyrij, Caza Baabda; Early Cretaceous (D. Azar coll.).

Discussion. Following the key to Holarctic subfamilies of Oliver and Dillon (1989) and to Palaearctic subfamilies in Saether et al. (2000), Libanodiamesa gen. n. falls in the Prodiamesinae because of the combination of the following characters: wing macropterous; MCu present; R 2+3 present, simple; wing membrane without setae; FCu distal to MCu. Furthermore, Libanodiamesa has bare eyes, unlike most recent Diamesinae Kieffer, 1923 .

Among the non-Holarctic subfamilies, affinities with the Aphroteniinae are excluded because Libanodiamesa has retained MCu and R 2+3, but it has a narrow space between R 4+5 and the costa. In the Usambaromyiinae, MCu is absent. The Chilenomyiinae have a MCu in a basal position (less basal than in Libanodiamesa ), but no R 2+3. Furthermore, unlike Libanodiamesa , their wings are uniformly covered with dense hair.

Within the Prodiamesinae , Libanodiamesa differs from all recent genera in the much more basal position of MCu, located midway between base of M and RM, and in the R 4+5, which ends well basad of the wing apex (Saether 1989). The lack of genital organs in the holotype of Libanodiamesa renders it impossible to predict the relationship of this genus with the other recent genera. Libanodiamesa and Cretadiamesa gen. n. (see below) are the oldest representatives of the subfamily Prodiamesinae .

Genus Cretadiamesa gen. n.

Etymology: After Cretaceous and Diamesa .

Type species: Cretadiamesa arieli sp. n., by present designation.

Diagnosis: Closely similar to Libanodiamesa ; the differences with this genus being as follows: veins R 1 and R 4+5 strongly approximate; R 2+3 very weakly indicated; apex of R

4+5

near wing apex; costa ending near wing apex.

Figures

Figs 15–17. Libanodiamesa deploegi gen. et sp. n., holotype 66: (15) general habitus; (16) forewing; (17) details of forewing venation. Scale bars = 0.5 mm.