Mesoplecia fastigata, Lin, Xiuqin, Shih, Chungkun & Ren, Dong, 2014

Lin, Xiuqin, Shih, Chungkun & Ren, Dong, 2014, Two new species of Mesoplecia (Insecta: Diptera: Protopleciidae) from the late Middle Jurassic of China, Zootaxa 3838 (5), pp. 545-556 : 552-554

Mesoplecia fastigata sp. nov.

( Figs. 6 A–6E)

Diagnosis. A combination of these characters: crossvein sc-r present; Sc reaching anterior margin at the level of rm; R2+3, sigmoidly curved, reaching anterior margin distad of the position of R1 apex; bRs 1.2 times as long as dRs; and dM1+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); R1 straight; Rs arising from R1 at basal one-third of wing length, furcating slightly distad of the level of M1+2 forking; pterostigma close to oval; bRs about 3.7 times as long as r-m; R4+5, weakly curved upward medially, approximately 1.8 times as long as R2+3, and almost equal to the basal part of Rs (bRs+dRs); M1, longer than M2, almost equal to M3+4; M2 about 5.3 times as long as dM1+2; m-cu well developed; CuA strongly curved, ending at posterior margin proximad of mid wing in the left wing ( Figs. 6 B, E). A1 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; 1st tarsomere shorter than tibia as preserved on the right foreleg, 2nd to 5th 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; 1st to 5th tarsomeres well developed with two pretarsal claws.

Abdomen: Sternites in segments 1–7 clearly visible in ventral view. The 1st sternite significantly narrower than the 2nd; the 3rd to 5th sternite widest, the 8th 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); R2+3 reaching anterior margin slightly distad of R1 apex (vs. R2+3 reaching anterior margin very close to the position of R1 apex) and dM1+2 longer than r-m (vs. shorter). Comparisons with other species are listed in the Table 1 .

Type material. Holotype, ♀, No. CNU-DIP-NN2013101 ( 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-NN2013101. 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; R1 3.2; R2+3 1.6; Rs 2.0; bRs 1.1; dRs 0.93; R4+5 3; rm 0.3; m-cu 0.32; bM1+2 0.6; dM1+2 0.47; M1 3.2, M2 2.5; pterostigma: length 1, width 0.48.

Key to Mesoplecia Rohdendorf, 1938 (see also comparison data summarized in Table 1 )

1. bM1+2 about 2.5 times as long as dM1+2..................................................................... 2

- bM1+2 clearly less than 2.5 times as long as dM1+2............................................................. 3

2. R2+3 long, slightly sigmoidly curved, reaching anterior margin distad of R1 apex............ M. jurassica Rohdendorf, 1938

- R2+3 short, significantly sigmoidly curved, reaching anterior margin very close to the position of R1 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; bM3+4 almost perpendicular to base of M1+2; cell ba slightly wider than cell bp termi- nally............................................................................ M. sibirica Kovalev, 1985

- Crossvein r-m almost as long as m-cu; bM3+4 oblique to base of M1+2; cell ba distinctly wider than cell bp terminally....... 5

5. Coastal field wide; wing narrow; R4+5 and M1 subparallel; femur robust, distinctly thicker than tibia.................................................................................................. M. anfracta Hao & Ren, 2009

- Coastal field narrow; wing broad; R4+5 and M1 convergent; femur slender, slightly thicker than tibia.................................................................................................. M. coadnata Hao & Ren, 2009

6. bM1+2 longer than dM1+2; dM1+2 shorter than r-m.............................................................. 7

- bM1+2 as long as dM1+2; dM1+2 longer than r-m............................................ M. mediana Zhang, 2007

7. bRs 2 times as long as dRs; R2+3 as long as bRs and dRs combined.............................. M. sinica Zhang, 2007

- bRs less than 2 times as long as dRs; R2+3 shorter than bRs and dRs combined...................................... 8

8. R2+3, reaching anterior margin distad of R1 apex.............................................. M. fastigata sp. nov.

- R2+3, reaching anterior margin very close to the position of R1 apex.............................................. 9

9. Crossvein sc-r present; bM1+2 significantly less than 2.2 times as long as dM1+2; dM1+2 longer than r-m.................................................................................................. M. stigma Rohdendorf, 1962

- Crossvein sc-r absent; bM1+2 about 2.2 times as long as dM1+2; dM1+2 shorter than r-m................... M. plena sp. nov.

Figures

FIGURE 6. Holotype of Mesoplecia fastigata sp. nov. (CNU-DIP-NN 2013101). A—Photograph of Holotype; B—Photograph (under alcohol); C—Enlarged details of right wing (under alcohol); D—Line drawing of right wing; E—Line drawing of Holotype. Scale bars = 1 mm.