Many Jurassic fossil nemestrinid flies have been found in the Palaearctic region. China is an important locality for fossil nemestrinid flies. Up to now, 2 genera with 3 species have been discovered in China. In the present paper, a third genus and species, Ahirmoneura neimengguensis Zhang, Yang, and Ren, gen. et sp. nov., from the Middle Jurassic Daohugou Formation of China is described. A key to genera of fossil nemestrinid flies from China is given.
Introduction
The family Nemestrinidae (tangle-veined flies) is a cosmopolitan group of brachyceran Diptera consisting of about 300 described species in over 20 genera. They are found in all Zoogeographic regions, most abundant and diverse in the Palaearctic, Australian, and Afrotropical regions, sparse in the Nearctic region. All known nemestrinid larvae are parasites of grasshoppers and scarabaeid beetle larvae. Bernardi (1973) have summarized the genera of Nemestrinidae around the world, including the morphology and distribution of fifteen extant and five fossil genera belonging to six subfamilies. Before this paper, 12 genera and 28 species of fossil Nemestrinidae have been described (Bequaert 1936; Bernardi 1973; Evenhuis 1994; Ren 1998; Mostovski 1998; Ansorge and Mostovski 2000; Mostovski and Martínez-Delclòs 2000). They have been found from the Jurassic to Tertiary of Germany, Kazakhstan, China, Spain, Russia, and USA. Besides, the genera Rhagionemestrius Ussatchev, 1968 and Sinonemestrius Hong and Wang, 1990 were removed from the family Nemestrinidae by Nagatomi and Yang (1998) as two independent families, Rhagionemestriidae and Sinonemestriidae.
Fig. 1.
Location of the type locality of Ahirmoneura neimengguensis Zhang, Yang, and Ren, gen. et sp. nov. Daohugou Village, Shantou Township, Ningcheng County, Inner Mongolia, China. A. Outlined location. B. Detailed location. Abbreviations: Chc, Changchougou Formation; Chch, Chuanlinggou Formation; Chd, Dahongyu Formation; Cht, Tuanshanzi Formation; J2j, Jiulongshan Formation; J2t, Tiaojishan Formation; Ky, Yixian Formation; Q, Quaternary; Dms, Dalaiyingzi erosion surface; Mgn, Maanshan gneiss.
Ren (1998) found 2 genera and 3 species of fossil Nemestrinidae for the first time from Western Liaoning of China. These are Florinemestrius pulcherrimus Ren, 1998, Protonemestrius jurassicus Ren, 1998, Protonemestrius beipiaoensis Ren, 1998. These two genera were discovered from the Late Jurassic Yixian Formation of Beipiao City, Liaoning Province. In the present paper, we describe the oldest nemestrinid from China from the Middle Jurassic (Aalenian-Bajocian) deposits of Jiulongshan Formation (Daohugou Village, Shantou Township, Ningcheng County, Inner Mongolia Province). During the past several years, the Daohugou locality (Fig. 1) became famous of excellently preserved animal and plant fossils known as Daohugou biota. The palaeoenvironmental reconstructions of the Daohugou site, suggest humid and warm-temperate climate for this volcanic region with mountain streams (Ren and Krzeminski 2002; Ren et al. 2002; Liu et al. 2004).
Other abbreviations.
bm, basal medial;
br, basal radial;
C, costa;
CuA1, CuA2, anterior branches of cubitus;
d, discal;
M1, M2, M3, posterior branches of media;
m1, m2, m3, medial;
R1, anterior branch of radius;
R2, R4, R5, posterior branches of radius;
r1, r2, r4, r5, radial;
r-m, radial-medial;
Rs, radial sector;
Sc, subcosta;
sc, subcostal.
Systematic palaeontology
Basic terminology follows McAlpine (1981) and Teskey (1981).
Order Diptera Linné, 1758
Family Nemestrinidae Macquart, 1834
Genus Ahirmoneura Zhang, Yang, and Ren, nov.
Type species: Ahirmoneura neimengguensis Zhang, Yang, and Ren, sp. nov.
Derivation of the name: The generic name refers to the difference between the new genus and Hirmoneura.
Diagnosis.—Body large. Eyes large, dichoptic, ommatidia clearly visible. Wing elongate and rather narrow: Base of vein C swollen and sclerotized with dense setulae. Vein Sc short, ending slightly beyond middle of wing, far from level of fork of vein R4+5. In apical part of wing, veins running parallel to anterior margin, ending before wing-tip. Vein R3 absent; vein R4 cambered basally. Crossvein r-m located at extreme base of cell d. Vein M2 arising from apex of cell d; veins M3 and CuA1 fused before wing margin with a petiole. Vein CuA1 arising from apex of cell d. Abdomen incomplete, 4 segments preserved. Segment I widest.
Remarks.—Judging from the wing venation, Ahirmoneura gen. nov. is similar to Hirmoneura Meigen, 1820 by having crossvein r-m present, vein M2 reaching the anterior margin of the wing, veins M3 and CuA1 fused before wing margin with a petiole, alula broad. But, the new genus differs from Hirmoneura in vein Sc ending slightly beyond the middle of the wing, crossvein r-m at the extreme base of cell d, vein Rs distinctly longer than the distance between vein R2 and crossvein r-m, vein M2 arising from the apex of cell d, the mouth of cell r1 over twice as long as that of cell r2, cell r4 longer than cell m1, cell br much shorter than cell bm. In Hirmoneura, vein Sc is ending far beyond the middle of the wing, crossvein r-m is located at the apical part of cell d, vein Rs is distinctly shorter than the distance between vein R2 and crossvein r-m, vein M2 is arising from cell m3, the mouth of cell r1 is less than twice as long as that of cell r2, cell r4 is shorter than cell m1, cell br is much longer than cell bm.
Key to genera of fossil (Jurassic) nemestrinid flies from China:
1. Crossvein r-m at extreme base of cell d; vein M2 arising from cell d Ahirmoneura
—. Crossvein r-m at apical part of cell d; vein M2 arising from cell m3 2
2. Crossvein between veins M1 and M2 present; veins M2 and CuA1 + M3 converged at a point at base Florinemestrius
—. Crossvein between veins M1 and M2 absent; veins M2 and CuA1 + M3 diverged at base Protonemestrius
Distribution.—The genus is known only from China and is currently represented by one species.
Ahirmoneura neimengguensis Zhang, Yang, and Ren, sp. nov.
Fig. 2.
Derivation of the name: After the type region: Inner Mongolia (Chinese pronunciation is “nei meng gu”).
Holotype: CNU-B-NN2006003, an almost complete adult body with wings in dorsal view.
Type locality: Daohugou Village, Shantou Township, Ningcheng County, Inner Mongolia, China.
Type horizon: Aalenian-Bajocian Jiulongshan Formation, Middle Jurassic.
Material.—Only holotype specimen.
Dimensions.—Body length over 22.5 mm, wing length 15.5 mm, wing width 5.0 mm.
Diagnosis.—The same as for the genus.
Description.—A large, dark fly. Head hemispherical in dorsal view, without hairs. Eyes large; dichoptic, ommatidia visible clearly. Antenna and proboscis not preserved.
Only anterior part of thorax preserved. Legs partly visible with dense pubescence. Wing elongate, rather narrow, pubescent; supernumerary crossvein absent. Base of vein C distinctly swollen, sclerotized with dense setulae. Vein Sc short, ending slightly beyond middle of wing, far from level of fork of vein R4+5. In apical part of wing, veins running parallel to anterior margin, ending before wing-tip. So-called diagonal vein (consisting of elements of Rs, common stem of veins R4 and R5, crossvein r-m, M1, M2, M3, and CuA1) absent. Vein R with four branches, vein R3 absent; base of vein R4 cambered. Crossvein r-m located at extreme base of cell d. Veins M1 and M2 diagonal and parallel; vein M2 arising from apex of cell d, ending slightly before wing tip; veins M3 and CuA1 fused before wing margin with a petiole. Crossvein m-cu absent. Vein CuA1 arising from apex of cell d. Vein CuA2 shorter than 1/2 of cell bm. Apex of vein A not preserved. Mouth of cell sc longer than that of cell r1. Mouth of cell r1 longer than wing margin between veins R2 and R5. Mouth of cells r4, r5, m1 subequal in length. Cell r4 longer than cell m1. Cell br short and small, apical portion of cell br narrow but unpointed. Cell d longer than cell m3. Five posterior cells present, cell m1 shorter than cell m2, cell m3 closed far before wing margin with a petiole. Anal lobe narrow. Alula broad.
Fig. 2.
Nemestrinid fly Ahirmoneura neimengguensis Zhang, Yang, and Ren, gen. et sp. nov., holotype CNU-B-NN2006003, from the Daohugou Village, Inner Mongolia, China; Aalenian-Bajocian Jiulongshan Formation, Middle Jurassic. A. Body with wings photograph in dorsal view. B. Camera lucida drawing, based on the original photograph, in dorsal view. C. Camera lucida drawing, base of vein C details.
Abdomen robust, covered with setulae. Abdomen incomplete, 4 segments preserved, apex not preserved. Segment I widest, abdomen segments narrowing toward tip. Gender unknown.
Discussion
The presence of so-called diagonal veins is the most conspicuous diagnostic character in most nemestrinid flies, including all known extinct genera. Ahirmoneura gen. nov. is unique among Nemestrinidae in lacking so-called diagonal veins, crossvein r-m located at the extreme base of cell d, vein M2 arising from cell d, cell m3 ending before cell d. These unusual characters, which are different from the extant genera and other extinct genera of Nemestrinidae, might be the plesiomorphies. Some similar states also have been observed in Sinonemestrius Hong and Wang, 1990. It provides evidence on how the composite “diagonal vein” was assembled over evolutionary time. Especially, the positional transformation of crossvein r-m and cell m3 plays a vital part in the progress of the venational evolution of family Nemestrinidae.
Acknowledgments
We are greatly indebted to David K. Yeates (CSIRO Entomology, Canberra, Australia) and Mikhail B. Mostovski (The Natal Museum, Pietermaritzburg, South Africa) for insightful comments on the manuscript. This research was supported by the National Natural Science Foundation of China (No. 30430100, 30225009, 30025006), PHR Project of Beijing Municipal Commission of Education.
