Spinorthocladius enigmaticus, Published, 2007

Published, First, 2007, Chironomid midges from early Eocene amber of France (Diptera: Chironomidae), Zootaxa 1404, pp. 1-66 : 26-27

Spinorthocladius enigmaticus n. sp.

( Fig. 22)

Etymology: This species is named after the enigmatic affinities of this taxon within the Orthocladiinae . Diagnosis: Same as that for the genus.

Description: Head deformed, 0.32 mm long; ocelli absent; antenna 0.44 mm long, much longer than head, distinctly hairy, with 13 flagellomeres covered with long setae (shortest 0.01 mm long, longest 0.4 mm long), pedicel broad and short, rounded, 13th flagellomere very long; eyes bare, with small dorsomedial extension, with 3 rows of ommatidia at minimum width; mouthparts lacking functional mandibles; 5 palpomeres with numerous setae; clypeus with few dorsal setae; 4 postocular setae, few outer vertical setae, frontal and inner vertical setae absent. Thorax 0.8 mm long, 0.84 mm high; postnotum bare, with visible longitudinal median groove; surface of scutellum with 8 long setae; scutal tubercle absent; acrostichals absent, dorsocentrals biserial; scutum without median longitudinal groove; 3 prealar and 1 supraalar setae; epimeron II, posterior mesanepisternum II and dorsal antepronotum bare. Wing macropterous, 1.4 mm long, 0.42 mm wide, hyaline, membrane bare; anal vein An 2 absent; radius with 3 branches R 1, R 2+3 and R 4+5, R 2+3 not divided; costa ending just beyond insertion of last branch of radius, produced by 0.05 mm, less than length of crossvein RM (0.08 mm); only M 1+2 and M 3+4 present; cross­vein MCu absent; anal lobe well developed; squama fringed. Halter 0.2 mm long. Fore femur 0.64 mm long, tibia 0.74 mm long, tarsus 1.1 mm long; mid femur 0.6 mm long, tibia 0.66 mm long, tarsus 0.8 mm long; hind femur 0.66 mm long, tibia 0.8 mm long, tarsus 1.02 mm long; ta4 of all legs cylindrical, not cordiform; fore tibia with 1 long spur, mid and hind tibiae with 2 long spurs; presence of well­developed hind tibial comb; ta1 and ta2 of mid and hind tibiae with 2 strong spurs, claw on all legs simple; pulvilli absent. Abdomen 1.4 mm long, 0.2 mm wide; gonostylus 0.1 mm long, 0.03 mm wide, hinged to gonocoxite and folded inward, with apical megasetae; 1 strong spur at apex of gonocoxite, gonocoxite (0.14 mm long and 0.06 mm wide) with long setae; anal point present, but very small and reduced.

Discussion: In the key to dipteran families of McAlpine (1981), these fossils fall in the family Chironomidae . In the keys to Nearctic genera of Oliver (1981), the key to Holarctic subfamilies of Oliver & Dillon (1989), and the key to Palaearctic subfamilies in Saether et al. (2000), Spinorthocladius n. gen. falls 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. Spinorthocladius n. gen. does not correspond to any of the described recent genera because it has one strong spur at the apex of the gonocoxite (see list of Ashe (1983) for old genera, and the two internet sites: http://animaldiversity.ummz.umich.edu/site/accounts/classification/ and http://www.itis.usda.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value= 128475). The phylogenetic relationships of Spinorthocladius n. gen. within the Orthocladiinae cannot be established because the current phylogenies of this subfamily are based on a combination of characters of the adult, larva, and pupa ( Brundin 1956; Saether 1976, 1977a). Spinorthocladius n. gen. can be separated from the oldest fossil genus Lebanorthocladius Veltz et al., 2007 (Early Cretaceous Lebanese amber) by the same characters ( Veltz et al., 2007). Meunier (1916) established the Baltic amber genus Cricotopiella , based on a single female, but it is poorly described and was not treated in a revision of Baltic amber Chironomidae by Seredszus (2003). He indicated that it is similar to the recent genus Cricotopus Wulp, 1874 . It is impossible to compare it to Spinorthocladius n. gen., except for its smaller size (body 1.25 mm long, instead of 2.40 mm in Spinorthocladius n. gen.).

Material: Holotype PA 2355, paratype PA 1742 (4/6), both males.