(Figs. 6 A– 6 E)
Diagnosis. A combination of these characters: crossvein sc-r present; Sc reaching anterior margin at the level of rm; R 2 + 3, sigmoidly curved, reaching anterior margin distad of the position of R 1 apex; bRs 1.2 times as long as dRs; and dM 1 + 2 longer than r-m.
Etymology. The specific name is derived from Latin word “fastigatus”, indicating the forelegs of the specimen with upraised posture.
Description. Thorax: The boundary among prothorax, mesothorax and metathorax not distinct in ventral view (Fig. 6 A); the right halter small.
Wing: Wing narrow and long (length: 7 mm, width: 2.8 mm); humeral vein h well developed, straight and short (Figs. 6 C, D); Sc well-developed, reaching anterior margin at the same level with r-m, crossvein sc-r present, located in the middle of Sc (Figs. 6 C, D); R 1 straight; Rs arising from R 1 at basal one-third of wing length, furcating slightly distad of the level of M 1 + 2 forking; pterostigma close to oval; bRs about 3.7 times as long as r-m; R 4 + 5, weakly curved upward medially, approximately 1.8 times as long as R 2 + 3, and almost equal to the basal part of Rs (bRs+dRs); M 1, longer than M 2, almost equal to M 3 + 4; M 2 about 5.3 times as long as dM 1 + 2; m-cu well developed; CuA strongly curved, ending at posterior margin proximad of mid wing in the left wing (Figs. 6 B, E). A 1 reaching the posterior margin in the left wing (Figs. 6 B, E).
Legs: The coxae of forelegs and right hind leg expanded (Fig. 6 E). Forelegs: femur and tibia well-preserved, femur distinctly thicker than tibia, covered with dense setae; 1 st tarsomere shorter than tibia as preserved on the right foreleg, 2 nd to 5 th tarsomeres not preserved; Mid legs: only right tibia well-preserved, tibia long and slender, tibial spur not preserved. Right hind leg well-preserved; femur cylindrical and thick; tibia slightly less than 2 times as long as femur; two tibial spurs well-developed; 1 st to 5 th tarsomeres well developed with two pretarsal claws.
Abdomen: Sternites in segments 1–7 clearly visible in ventral view. The 1 st sternite significantly narrower than the 2 nd; the 3 rd to 5 th sternite widest, the 8 th sternite combined with genitalia undivided, with cerci apically.
Remarks. The new species is similar to M. plena sp. nov., but can be distinguished from the latter by crossvein sc-r present (vs. absent); R 2 + 3 reaching anterior margin slightly distad of R 1 apex (vs. R 2 + 3 reaching anterior margin very close to the position of R 1 apex) and dM 1 + 2 longer than r-m (vs. shorter). Comparisons with other species are listed in the Table 1.
Type material. Holotype, ♀, No. CNU-DIP-NN 2013101 (Fig. 6), an almost completely preserved specimen of a female in ventral view, with well-preserved abdomen, the wing clearly visible as preserved. The type specimen is deposited in the Key Laboratory of Insect Evolution and Environmental Changes, Capital Normal University.
Measurements (in mm). Holotype: ♀, CNU-DIP-NN 2013101. Body length (excluding head which is not preserved) 7.7, maximal width of body 1.5; Foreleg: femur 1.6; tibia 2.0. Mid leg: femur 0.8 (as preserved); tibia 2.3. Hind leg: femur 1.8; tibia 3.2. Wing: length 7.0, width 2.8; R 1 3.2; R 2 + 3 1.6; Rs 2.0; bRs 1.1; dRs 0.93; R 4 + 5 3; rm 0.3; m-cu 0.32; bM 1 + 2 0.6; dM 1 + 2 0.47; M 1 3.2, M 2 2.5; pterostigma: length 1, width 0.48.
Key to Mesoplecia Rohdendorf, 1938 (see also comparison data summarized in Table 1)
1. bM 1 + 2 about 2.5 times as long as dM 1 + 2..................................................................... 2
- bM 1 + 2 clearly less than 2.5 times as long as dM 1 + 2............................................................. 3
2. R 2 + 3 long, slightly sigmoidly curved, reaching anterior margin distad of R 1 apex............ M. jurassica Rohdendorf, 1938
- R 2 + 3 short, significantly sigmoidly curved, reaching anterior margin very close to the position of R 1 apex................................................................................................ M. oleynikovi Kovalev, 1990
3. Sc reaching anterior margin proximad of r-m and near the middle of bRs.......................................... 4
- Sc reaching anterior margin at the same level as r-m.......................................................... 6
4. Crossvein r-m distinctly longer than m-cu; bM 3 + 4 almost perpendicular to base of M 1 + 2; cell ba slightly wider than cell bp termi- nally............................................................................ M. sibirica Kovalev, 1985
- Crossvein r-m almost as long as m-cu; bM 3 + 4 oblique to base of M 1 + 2; cell ba distinctly wider than cell bp terminally....... 5
5. Coastal field wide; wing narrow; R 4 + 5 and M 1 subparallel; femur robust, distinctly thicker than tibia.................................................................................................. M. anfracta Hao & Ren, 2009
- Coastal field narrow; wing broad; R 4 + 5 and M 1 convergent; femur slender, slightly thicker than tibia.................................................................................................. M. coadnata Hao & Ren, 2009
6. bM 1 + 2 longer than dM 1 + 2; dM 1 + 2 shorter than r-m.............................................................. 7
- bM 1 + 2 as long as dM 1 + 2; dM 1 + 2 longer than r-m............................................ M. mediana Zhang, 2007
7. bRs 2 times as long as dRs; R 2 + 3 as long as bRs and dRs combined.............................. M. sinica Zhang, 2007
- bRs less than 2 times as long as dRs; R 2 + 3 shorter than bRs and dRs combined...................................... 8
8. R 2 + 3, reaching anterior margin distad of R 1 apex.............................................. M. fastigata sp. nov.
- R 2 + 3, reaching anterior margin very close to the position of R 1 apex.............................................. 9
9. Crossvein sc-r present; bM 1 + 2 significantly less than 2.2 times as long as dM 1 + 2; dM 1 + 2 longer than r-m.................................................................................................. M. stigma Rohdendorf, 1962
- Crossvein sc-r absent; bM 1 + 2 about 2.2 times as long as dM 1 + 2; dM 1 + 2 shorter than r-m................... M. plena sp. nov.