Revision of the genus Epimesoplecia Zhang, 2007 (Diptera, Nematocera, Protopleciidae) with five new species

Abstract The genus Epimesoplecia Zhang, 2007 of Protopleciidae is revised based on five new species, Epimesoplecia plethora sp. n., Epimesoplecia prosoneura sp. n., Epimesoplecia stana sp. n., Epimesoplecia macrostrena sp. n., and Epimesoplecia ambloneura sp. n., described and illustrated from the Jiulongshan Formation of China. These new species, with clearly preserved characters of (1) compound eyes connected in males; (2) antennae, filiform or moniliform, with 16 segments; (3) r-m reaching the middle of the wing; (4) R4+5 ending very close to wing apex; (5) ratio of bRs/dRs ranging from 1.6 to 10.5; (6) M2 more than 3 times as long as dM1+2; (7) legs thin and long, femur slender, almost equal to tibia; (8) tibial spurs minute; and (9) male genitalia (previously unknown), enable us to emend the diagnosis of Epimesoplecia Zhang, 2007. In addition, all described species of Epimesoplecia are characterized, their features summarized, and a key to Epimesoplecia species is given.


Introduction
. The paleoenvironment reconstructed for that time was a volcanic region with mountains, streams and lakes under a humid and warm climate (Ren et al. 2002;Gao and Ren 2006).

Material and methods
All the type materials were collected from the Jiulongshan Formation (Fig. 1A) of Daohugou Village in Ningcheng County of Inner Mongolia, China (Fig. 1B) (after Ren et al. 2002). The specimens are housed in the Key Laboratory of Insect Evolution and Environmental Changes, College of Life Sciences, Capital Normal University, Beijing, China (CNUB; Dong Ren, Curator). The specimens were examined and photographed using a Leica MZ12.5 dissecting microscope with a Leica DFC 500 digital camera and illustrated with the aid of camera lucida attached to the microscope. The line drawings were drawn by Adobe Photoshop CS5. The wing venation nomenclature used in this paper is based on the interpretations and system proposed by Shcherbakov et al. (1995) and Wootton and Ennos (1989).
Revised diagnosis. Compound eyes connected in males. Antennae filiform or moniliform, with 16 segments, at least twice of head length or slightly less than twice of head length; wings narrow and long; Sc elongate, at or near the same level of r-m; bRs at least 4 times as long as r-m; R 2+3 long, more than two-thirds of R 4+5 , R 2+3 slightly sigmoidly curved or straight, reaching anterior margin distad of the apex of R 1 ; r-m reaching the middle of the wing; R 4+5 ending very close to wing apex; M 1+2 furcated distinctly proximad or distad of R 2+3 ; M 2 more than 3 times as long as dM 1+2 ; bM 3+4 longer or slightly shorter than m-cu; pterostigma absent; bM 1+2 longer or shorter than dM 1+2 . Legs thin and long, femur slender, almost equal to tibia; tibial spurs minute. Male genitalia: abdomen cylindrical; genitalia complex, narrower than the 8th segment, with gonocoxites rounded; gonostylus elongated, shorter than gonocoxites. Female genitalia: the 8th segment smaller than preceding segments, genitalia simple, with 2-segmented cerci, the basal segment of cerci longer than the terminal one. Etymology. The epithet of plethora is derived from the Greek word "plethore", meaning "fullness", emphasizing the body covered with dense pubescence. The specific epithet is a noun in apposition.
Diagnosis. Compound eyes crescent. Antennae moniliform. Sc very close to the level of r-m; fork of Rs distad of fork of M 1+2 ; Rs distad of crossvein r-m; bRs less than 2 times (1.6-1.8) as long as dRs, the latter about 3 times (2.6-3) as long as r-m; R 2+3 , sigmoidly curved, distinctly shorter than bRs and dRs combined; bM 1+2 shorter than dM 1+2 ; bM 3+4 shorter than m-cu; cell bp as wide as cell ba terminally.
Horizon and locality. All specimens were collected from the Jiulongshan Formation, late Middle Jurassic age (Late Callovian) from Daohugou Village, Ningcheng County, Inner Mongolia Autonomous Region in China.
Legs (Figs 2A, 3A, B): Forelegs comparatively thin and slender, femur slightly thicker than tibia, covered with dense setae as preserved. The 1st tarsomere 2 times as long as the 2nd tarsomere; the 3rd to 5th tarsi gradually thinned, claws small. Mid legs: femur long and slender, almost equal to tibia, tibial spurs minute, claws well-preserved. Hind legs: femur more than four-fifths of tibia; distinctly longer than forelegs and mid legs, tibia less than 2 times as long as femur; the 1st tarsomere more than 2 times as long as the 2nd tarsomere; with two pretarsal claws.
Wings (Figs 2A,C and 3A): Wing long and narrow, 2.6-2.8 times as long as width (length 8.4-9.0 mm, width 3.0-3.4 mm); Sc terminating at the middle of the anterior margin, the costal field narrow; bRs 4-5 times as long as r-m; R 2+3 slightly sigmoidly curved; Rs arising from one-fourth of wing length, furcating distal level of fork of M 1+2 ; stem of Rs longer than stem R, the former longer than R 2+3 ; R 4+5 weakly curved upward medially, ending just below apex of wing; both R 4+5 and M 1 subparallel; crossvein m-cu as long as r-m; CuA strongly curved, distad of M forking, ending at posterior margin of wing; A 1 not preserved.
Female genitalia (Fig. 2E, G): The 8th segment slightly smaller than preceding segments, genitalia simple, with 2-segmented cerci, the basal segment of cerci thicker and longer than the terminal one.  Remarks. The new species is differentiated from E. shcherbakovi Zhang, 2007 by the following features: bRs less than 2 times (1.6-1.7) as long as dRs (vs. bRs 4.5 times as long as dRs); Rs bifurcation distad to fork of M 1+2 (vs. Rs bifurcation at the same level of fork of M 1+2 ); dM 1+2 longer than bM 1+2 (vs. dM 1+2 shorter than bM 1+2 ). The new species differs from E. elenae Zhang, 2007 in having antennae moniliform (vs. filiform); bRs short, less than 2 times (1.6-1.7) as long as dRs (vs. bRs long, 2.5 times as long as dRs); bM 3+4 clearly shorter than m-cu (vs. bM 3+4 as long as m-cu). Comparisons with other species are listed in Table 1.
Horizon and locality. All specimens were collected from the Jiulongshan Formation, late Middle Jurassic age (Late Callovian) from Daohugou Village, Ningcheng County, Inner Mongolia Autonomous Region in China.
Description. Head (Figs 4C and 5C): Oviform. Compound eyes protrusive in males. Antennae long, scape and pedicel thick and stout, the 1st flagellomere slender and long, the remaining ones becoming thinner toward apex.
Wings (Figs 4H and 5B): Wing long and narrow (length: 8-8.9 mm, width: 2.6-2.7 mm), apex of wings covering the abdominal terminalia. Costal field long and thin, Sc reaching C at the middle of anterior margin; Rs arising from basal one-fourth of wing length, furcating distad to fork of M 1+2 ; bRs about 5 times (4.8-5.7) as long as r-m; crossvein m-cu slightly longer than r-m; CuA slightly curved, ending at posterior margin distad of mid wing; vein A 1 nearly straight, reaching posterior margin.
Female genitalia (Fig. 5D): The 8th segment slightly smaller than preceding segments, genitalia simple, with 2-segmented cerci, the basal segment of cerci longer than the terminal one. Remarks. The new species is similar to E. shcherbakovi Zhang, 2007 but differs from the latter in having bRs about 10 times (9.4-10.5) as long as dRs (vs. 4.5 times); Rs bifurcation proximad of fork of M 1+2 (vs. Rs bifurcation at the same level of fork of M 1+2 ); dM 1+2 longer than bM 1+2 (vs. dM 1+2 shorter than bM 1+2 ); R 2+3 , very close to the position crossvein r-m, distinctly longer than bRs and dRs combined (vs. R 2+3 , distad of the position crossvein r-m, clearly shorter than bRs and dRs combined). The new species differs from E. plethora sp. n. in having bRs about 10 times (9.4-10.5) as long as dRs (vs. less than 2 times); bM 3+4 clearly shorter than m-cu (vs. bM 3+4 shorter than m-cu); Rs bifurcation proximad of fork of M 1+2 (vs. Rs bifurcation distad of fork of M 1+2 ); dRs distinctly shorter than r-m (vs. dRs about 3 times as long as r-m); R 2+3 , very close to the position crossvein r-m, distinctly longer than bRs and dRs combined (vs. R 2+3 , sigmoidly curved, distinctly shorter than bRs and dRs combined). Comparisons with other species are listed in Table 1.
Diagnosis. Antennae moniliform. Sc very close to the level of r-m; fork of Rs distad of fork of M 1+2 ; R 2+3 distad of crossvein r-m; R 2+3 , straight, distinctly less than bRs and dRs combined; bRs 2.5 times as long as dRs, the latter 2 times as long as r-m; bM 1+2 significantly longer than dM 1+2 (2.3 times); bM 3+4 slightly longer than m-cu; cell bp narrower than cell ba terminally.
Material. Holotype: female, NO. CNU-DIP-NN-2013201p/c, in lateral view, a well-preserved body with partial antennae, almost complete wings and legs.
Horizon and locality. The specimen was collected from the Jiulongshan Formation, late Middle Jurassic age (Late Callovian) from Daohugou Village, Ningcheng County, Inner Mongolia Autonomous Region in China.
Wings (Fig. 6F): Wing long and narrow, more than 3 times as long as width (length: 11.2 mm, width: 3.4 mm as preserved); apex of wings covering the abdominal terminalia. Costal field long and thin, Sc reaching C very close to the position of r-m; Rs arising from basal one-fourth of wing length, furcating distad to level of fork of M 1+2 . Stem of Rs longer than stem of R, the former longer than R 2+3 , bRs 5 times as long as r-m; crossvein r-m longer than m-cu; CuA slightly curved, ending at posterior margin; vein A 1 short, slightly longer than half of cell bp.
Remarks. The new species having ratio of bRs/dRs of 2.5 is similar to E. elenae Zhang, 2007, but is distinguished from the latter by having Rs bifurcation significantly distad of fork of M 1+2 (vs. Rs bifurcation slightly distad of fork of M 1+2 ); bM 1+2 distinctly longer than dM 1+2 (vs. bM 1+2 clearly shorter than dM 1+2 ); dM 1+2 clearly shorter than r-m (vs. dM 1+2 as long as r-m); dM 1+2 short, almost oneeighth of M 2 (vs. dM 1+2 long, one-fifth of M 2 ). Comparisons with other species are listed in Table 1.
Diagnosis. Antennae filiform. Sc very close to the level of r-m; fork of Rs proximad of fork of M 1+2 ; R 2+3 distad of crossvein r-m; R 2+3 , straight, slightly shorter than bRs and dRs combined; bRs about 5 times (4.2-5) as long as dRs, the latter almost equal to r-m; bM 1+2 shorter than dM 1+2 (0.7 times); bM 3+4 shorter than m-cu (barely longer than m-cu); cell bp slightly wider than cell ba terminally.
Horizon and locality. All specimens were collected from the Jiulongshan Formation, late Middle Jurassic age (Late Callovian) from Daohugou Village, Ningcheng County, Inner Mongolia Autonomous Region in China.
Legs (Figs 7A, B and 8E): Forelegs: femur thicker than tibia; almost four-fifths of tibia; the 1st tarsomere longer than half of tibia, the 2nd-5th greatly thinned than the former. Mid legs: femur slightly thicker than tibia; tibial spurs minute; the 1st tarsomere slightly longer than the 1st tarsomere of forelegs. Hind legs: femur expanded almost equal to tibia; tibial spurs minute; tarsi not preserved.
Wings (Figs 7E, 8D and F): Wing long and narrow (length: 7.1-8 mm, width: 2.3-3.2 mm), apex of wings not reaching the abdominal terminalia. Costal field long and thin, apex of Sc gradually tapering to the end; Rs arising almost from basal one- fifth of wing length, furcating proximad of fork of M 1+2 bRs 4.4-5.6 times as long as r-m; crossvein m-cu slightly shorter than r-m; CuA arched near anal margin; vein A 1 nearly straight, reaching posterior margin.

Dimensions (in mm).
[Measurements for the holotype in brackets]. Body length 7 (as preserved)-11.3 [10.3 as preserved]; antennae 0.9 (as preserved)-1.4 (segments 1-16) [0.9 segments 1-9]. Forelegs: femur 2. Remarks. The new species is similar to E. shcherbakovi Zhang, 2007, but is differentiated from the latter by having Rs bifurcation proximad of fork of M 1+2 (vs. Rs bifurcation at the same level of fork of M 1+2 ); bM 1+2 shorter than dM 1+2 (vs. bM 1+2 longer than dM 1+2 ); dRs as long as r-m (vs. dRs clearly shorter than r-m); dM 1+2 long, almost one-third of M 2 (vs. dM 1+2 short, significantly less than one-third of M 2 ). Comparisons with other species are listed in Table 1. Etymology. The epithet of ambloneura is derived from the Greek prefix "ambl-", meaning "obtuse", and Greek word "neura", meaning "string or sinew", referring to the blunt caudal vein of this species. The specific epithet is a noun in apposition. Diagnosis. Antennae filiform. Sc very close to the level of r-m; fork of Rs at the same level of fork of M 1+2 ; R 2+3 proximad of crossvein r-m; R 2+3 , straight, distinctly longer than bRs and dRs combined; bRs about 6-7 times as long as dRs, the latter clearly shorter than r-m; bM 1+2 significantly longer than dM 1+2 (1.3-2.8 times); M 2 8-11 times as long as dM 1+2 ; bM 3+4 shorter than m-cu; cell bp slightly wider than cell ba terminally.
Horizon and locality. All specimens were collected from the Jiulongshan Formation, late Middle Jurassic age (Late Callovian) from Daohugou Village, Ningcheng County, Inner Mongolia Autonomous Region in China.
Description. Head (Fig. 9C): Oviform and very small in lateral view; antennae long, with 16 segments, scape and pedicel slightly compressed; flagellar segments slender and long, becoming thinner and shorter toward apex; maxillary palpi segments barely visible.
Wings (Figs 9B and 10B): Wing long and narrow (length: 7.4-9.1 mm, width: 3.2-3.6 mm), apex of wings not reaching the abdominal terminalia. Costal field long and thin, apex of Sc gradually tapering to the end; Rs arising almost from basal onefifth of wing length, furcating at the same level of fork of M 1+2 ; bRs 5 times as long as r-m; CuA slightly oblique; vein A 1 nearly straight, not reaching posterior margin, exceeding the level of m-cu.
Female genitalia (Fig. 9D Remarks. The new species is similar to E. shcherbakovi Zhang, 2007, but differs from the latter in having bRs about 6-7 times as long as dRs (vs. 4.5 times); R 2+3 clearly longer than bRs and dRs combined (vs. R 2+3 significantly shorter than bRs and dRs combined); Rs bifurcation proximad of r-m (vs. Rs distad of r-m); M 2 8-11 times as long as dM 1+2 (vs. 5 times); bM 3+4 shorter than m-cu (vs. bM 3+4 longer than m-cu). Comparisons with other species are listed in the Table 1.

Discussion
The generic diagnosis of Epimesoplecia Zhang, 2007 is revised based on eleven wellpreserved new specimens, among which ten are used to describe the afore-mentioned five new species. One is identified as a new material for E. elenae Zhang, 2007 (Fig. 11), In total, seven species with 13 specimens have been described in Epimesoplecia so far, all from the Jiulongshan Formation of China (Table 1). It is interesting to note that only one of the 13 specimens reported so far is male, ie. the holotype of E. prosoneura sp. n. (CNU-DIP-NN2013207 p/c) with well-preserved male genitalia. We also describe a female paratype of E. prosoneura sp. n. (CNU-DIP-NN2013214) with well-preserved female genitalia. Since both specimens have similar body size, wing length and venational characters, the sexual dimorphism of this species seems to be not significant.
The measurements of body length, wing length and other important characters of wings are summarised in Table 1. The data and information suggest that the following characters are stable within a species, but differ among different species: (1) fork of Rs vs. fork of M 1+2 ; (2) ratio range of bRs and dRs; (3) dRs longer or shorter than r-m; (4) bM 1+2 longer or shorter than m-cu; and (5) antennae moniliform or filiform. Based on these taxonomic characters, a key to the species of Epimesoplecia Zhang, 2007 is provided.