A new genus with two new species of mesosciophilids from the Middle Jurassic of China (Diptera: Nematocera: Mesosciophilidae)

Mesosciophilidae is one of the extinct families of the suborder Nematocera in Diptera. Six genera and 17 species of mesosciophilids have so far been described from the Holarctic Region, including China, Kazakhstan, Kirghizia, Russia and Transbaikalia. Herein, a new genus with two new species, Similsciophila singularis gen. et sp. nov. and Similsciophila sinuata sp. nov. from the late Middle Jurassic, Jiulongshan Formation of Daohugou Village, Inner Mongolia, China, are described based on their venation and body characters. A new key to genera of mesosciophilid gnats is provided. http://zoobank.org/urn:lsid:zoobank.org:pub:8A772D35-29A8-49AA-9B7F-D9994992EE71


Introduction
Mesosciophilidae is an extinct family in Diptera. In 1946, Rohdendorf first described the members of Mesosciophilidae as a subfamily Mesosciophilinae within the family of Allactoneuridae (Rohdendorf 1946). Later, Allactoneuridae was renamed as Fungivoritidae (Rohdendorf 1964). In 1985, Kovalev thought that Fungivoritidae was a junior synonym of Pleciofungivoridae, and raised the subfamily Mesosciophilinae to the level of family Mesosciophilidae (Kovalev 1985). In 1993, Blagoderov revised the diagnosis of Mesosciophilidae, and erected the genus Mesosciophilopsis with three species from the Neocomian, Lower Cretaceous of Transbaykal, Baysa (Blagoderov 1993). In 2007, Zhang established the genus Paramesosciophilodes, and referred two species respectively to the genera of Mesosciophila and Paramesosciophilodes within the Mesosciophilidae from the Jiulongshan Formation in Daohugou, Chifeng, Inner Mongolia, China (Zhang 2007). Soon afterwards, Zhang reviewed all records of mesosciophilid gnats, added three species into three genera, and thought that a Chinese species Sinosciophila meileyingziensis Hong, 1992 might be a member of the Mesosciophilidae (Zhang 2008). In 2009, Li and Ren described the genus Jurasciophila with three species from the late Middle Jurassic Jiulongshan Formation of Daohugou in southeastern Inner Mongolia, China (Li and Ren 2009). In 2012, Wang et al. assigned two species to Mesosciophila and Paramesosciophilodes within Mesosciophilidae (Wang et al. 2012). To date, six genera and 17 species of mesosciophilids have been described from the Holarctic Region, and the majority of fossil mesosciophilids are described from the Middle or Late Jurassic, with some from the Early Cretaceous (Table 1) Based on a combination of unique wing venation characters of three well-with two new species, Similsciophila singularis sp. nov. and Similsciophila sinuata sp. nov. These specimens were collected from the late Middle Jurassic Jiulongshan Formation of Daohugou Village in the Ningcheng County, Chifeng City, southeastern Inner Mongolia, China. Many fossil insects have been described from this locality in recent years , such as mecopterans (Ren 1994), dipterans (Zhang et al. , 2011, neuropterans (Wang et al. 2010), orthopterans (Gu et al. 2012) andheteropterans (Yao et al. 2012).

Material and methods
This study is based on three specimens housed in the Key Lab of Insect Evolution & Environmental Changes, Capital Normal University, Beijing, China (Curator: Dong Ren). Line drawings were prepared from high-resolution photographs with CorelDraw 12 graphic software. Wing venation nomenclature is after Wootton and Ennos (1989); Shcherbakov et al. (1995); Mostovski (1997); Blagoderov et al. (2002) and Zhang (2008). In some literature, the anal vein A is called CuP. In this paper, vein A is used. Cell r length is measured from the forking point of bRs from R 1 to the forking point of R 2+3 from R 1 .

Diagnosis
Body medium-sized, covered with long and dense pubescence. Mesonotum convex. Scutellum sharp and clearly projecting. Forewing Sc elongate, shorter than one-half of wing length; sc-r situated distinctly basal to Rs origin, arising near midway between h to Sc ending at margin; cell r distinctly large, longer than one-sixth of wing length; Rs furcated distad to fork of M 1+2 ; bRs longer than r-m; R 1 slightly curved; both R 1 and R 4+5 divergent terminally; R 4+5 arched near its mid-length; stem of M not developed and thin; M 1+2 furcated slightly distad to level of Sc ending. Tibiae and tarsi with short sparse setae.

Etymology
The generic name is derived from the Latin (simil-), in reference to similar, and sciophila is from the generic name Mesosciophila.

Remarks
Based on the venation, Similsciophila gen. nov. is distinguished from Mesosciophilopsis Blagoderov, 1993 andJurasciophila Li andRen, 2009 by the following characters: wing longer and wider; cell r distinctly larger, and longer than one-sixth of wing length. The new genus is similar to the genus Paramesosciophilodes Zhang, 2007, but differs mainly by bRs longer than r-m. It also differs from Mesosciophilina Kovalev, 1985, Mesosciophilodes Rohdendorf, 1946and Mesosciophila Rohdendorf, 1946 in that R 4+5 arched near its mid-length.

Distribution
China.
Key to genera of mesosciophilid gnats

Material
Holotype No. CNU-DIP-NN2011226, a well-preserved complete body with a haltere and two wings. Paratype No. CNU-DIP-NN2011147 p/c, a specimen in lateral aspects with part of wings overlapping.

Etymology
The specific name is from the Latin (singularis), meaning single, for all the veins are single.

Description
Medium-sized mesosciophilid gnats, male adult, in dorsal aspects. Wings out-spread. Head poorly preserved. Antennae 19 segments (as preserved on Paratype), with all flagellomeres oblong and nearly the same size in length and width. Body covered with long dense pubescence. Mesonotum convex, scutellum clearly projecting. Abdomen thin, subcylindrical, about 2.7 times as long as head and thorax combined, with eight abdominal segments, first five segments gradually widened distally, sixth, seventh and eighth gradually narrowed terminally. Male genitalia relatively small, distinctly narrower than eighth abdominal segment. Haltere well-preserved, spatulate, and with its inner margin straight. Legs relatively thin and long, coxae and femora clavate; femora, tibiae and tarsi with two rows of sparse and short setae.  Wing membranous, oblong, darker in colour in costal area, 2.4 times as long as wide, and not reaching apex of abdomen at rest. C strong, ending beyond wing apex, at which R 4+5 ending. Sc long, about 0.4 times as long as wing (shorter than one-half of wing length), and ending far distal to crossing of bRs and r-m. h distinct, and curved. sc-r well developed, situated distinctly basal to Rs origin, arising near midway between h to Sc ending at margin. Cell r distinctly large, longer than one-sixth of wing length (about 0.2 times as long as wing length). The section of R from sc-r to Rs origin about 1.8 times as long as bRs. R furcated to three branches (R 1 , R 2+3 and R 4+5 ). Both R 1 and R 4+5 running somewhat divergent terminally. R 2+3 and R 4+5 arched. Forking of Rs beyond level of forking of M. Rs usually strongly furcated, arising from less than basal one-third of length of wing, with nearly 0.4 times as long as R 4+5 , basal near to midwing to R 2+3 and R 4+5 , but furcated distad to fork of M 1+2 . bRs significantly long, and 1.3 times as long as r-m. R 1 slightly curved, relatively long (nearly 0.7 times of length of wing). R 2+3 slightly curved, beyond level of M 1+2 forking, almost perpendicular to R 4+5 . R 4+5 strongly arched near its midway. Stem of M not developed, thin, usually thinner than its branches, and furcated to M 1 , M 2 and M 3+4 . M 1 arched upwards, and subparallel to R 4+5 . M 2 nearly straight. r-m short, slightly oblique, nearly upright with M 1+2 , almost parallel to R 2+3 , intersected at M 1+2 , which furcated to bM 1+2 and dM 1+2 . dM 1+2 about 1.7 times as long as bM 1+2 , and longer than r-m. bM 1+2 about 2.3 times as long as m-cu. CuA running close to M 3+4 basally, but neither coalescent. Vein A short, slightly curved at its midway, ending far from posterior margin of wing.

Diagnosis
Wing membranous 2.2 times as long as wide; R 2+3 strongly curved, and usually strongly sigmoid; bRs long and about 2.0 times as long as r-m; dM 1+2 about 1.3 times as long as bM 1+2 ; bM 1+2 about 5.8 times as long as m-cu.

Material
Holotype No. CNU-DIP-NN2011511, an incomplete body with two wings and a haltere, in lateral aspects.

Etymology
The specific name is from the Latin (sinua-), meaning that vein R 2+3 is more arching.

Remark
This new species is differentiated from Similsciophila singularis gen. et sp. nov. by the following characters: (1) R 2+3 of the new species is strongly curved, and usually strongly sigmoid (versus slightly curved, almost perpendicular to R 4+5 ); (2) the ratio of bRs and r-m of the two species is diverse (2.0 versus 1.1-1.4); (3) the ratio of dM 1+2 and bM 1+2 of the two species is different (1.3 versus 1.4-1.8); (4) the ratio of bM 1+2 and m-cu of the two species is dissimilar (5.8 versus 2.0-2.4).

Description
Mesosciophilid gnats medium-sized, in lateral aspects. Wings outspread. Head poorly preserved. Antennae well-preserved, 13-segmented, longer than head, with all flagellomeres oblong and nearly the same size in length and width. Body covered with long dense pubescence. Mesonotum convex, scutellum sharp and clearly projecting. Abdomen incomplete preserved. A haltere well-preserved, spatulate, and its inner margin a bit straight. Legs thin long, clavate, and covered with two rows of sparse and short setae. Wing membranous, oblong, darker in colour in costal area, 2.2 times as long as wide, and not reaching apex of abdomen at rest. C strong, ending beyond wing apex, at which R 4+5 ending. Sc relatively long, about 0.4 times as long as wing, and ending far distal to crossing of bRs and r-m. h distinct. sc-r well developed, arising near midway between h to Sc ending at margin, and situated distinctly basal to Rs origin. Cell r distinctly large, longer than one-sixth of wing length, and nearly 0.2 times as long as wing length. The section of R from sc-r to Rs origin about 1.6 times as long as bRs. R furcated to three branches. R 1 slightly curved, relatively long, and about 0.6 times length of wing. R 1 and R 4+5 running divergent terminally. Rs robust, arising from less than basal one-third of length of wing, furcated basal near to midwing to R 2+3 and R 4+5 , and nearly 0.4 times as long as R 4+5 . bRs distinctly long, and 2.0 times as long as r-m. R 2+3 arched, strongly curved, and usually strongly sigmoid, beyond level of M 1+2 forking, almost perpendicular to R 4+5 . R 4+5 strongly arched near its midlength. R 4+5 and M 1 arched and subparallel. r-m short, slightly oblique, furcated M 1+2 to bM 1+2 and dM 1+2 , and shorter than dM 1+2 . Veins of bM 1+2 and r-m forming nearly a right angle. dM 1+2 about 1.3 times as long as bM 1+2 . M furcated to M 1 , M 2 and M 3+4 . Stem of M not developed, thin, and usually thinner than its branches. Forking of M beyond level of forking of Rs. M 1+2 furcated slightly distad to level of Sc ending. M 1 arched upwards, and subparallel to R 4+5 . M 2 almost straight. bM 1+2 about 5.8 times as long as m-cu. CuA running close to M 3+4 basally, but neither coalescent. A slightly curved at its midway, ending far from posterior margin of wing.

Discussion
To compare the difference of two key characters for various genera, we reviewed the previous work in literature and the two aforementioned new species and set up Table 2. The most remarkable generic features of Mesosciophilina (Kovalev, 1985), reported from the Middle Jurassic, are that cell r is distinctly large, longer than onesixth of wing length, and r-m is significantly shorter than bRs, which are regarded as 'obvious ancestral characters' (Zhang 2002). But, the generic features of Mesosciophilopsis (Blagoderov 1993), described from the Early Cretaceous, are cell r distinctly small, shorter than one-sixth of wing length, and r-m significantly longer than bRs, which are regarded as 'derived characters' (Zhang 2002). Furthermore, the generic features of Jurasciophila (Li and Ren, 2009), which was found in the late Middle Jurassic Jiulongshan Formation of China, have transitional characters of cell r small, shorter than one-sixth of wing length, and r-m significantly shorter than bRs (Li and Ren 2009). In comparison, the Similsciophila gen. nov., which was found in the late Middle Jurassic Jiulongshan Formation of China, has characters of cell r distinctly large, longer than one-sixth of wing length, and r-m from significantly to slightly shorter than bRs, bRs 1.1-2.0 times as long as r-m. Therefore, we infer that Similsciophila gen. nov. also has 'obvious ancestral characters'. shorter than 1/6 of wing length markedly shorter than bRs, bRs 1.6 times as long as r-m Mesosciophilopsis Early Cretaceous shorter than 1/6 of wing length markedly longer than bRs. bRs 0.6 times as long as r-m