Sinonemestrius completus, Zhang, Junfeng, 2017

Zhang, Junfeng, 2017, On the enigmatic Sinonemestrius Hong & Wang, 1990, with description of a new species based on a complete fossil fly (Diptera, Brachycera, Tabanomorpha, Heterostomidae), Deutsche Entomologische Zeitschrift 64 (1), pp. 61-67 : 61-63

Sinonemestrius completus sp. n. Figs 1, 2, 3

Diagnosis.

Similar to Sinonemestrius tuanwangensis , but R2+3 smoothly curved downwards and parallel to R1, ending at C instead of R1 end; fork of R4+5 distinctly distad to fork of M1+2; crossvein r-m meeting anterior margin of discal cell basad to its midlength; wing membrane with few markings (only limited to “Pt” and below it).

Description.

Male medium-sized flies. Female unknown. Head moderately large, semiglobose, slightly narrower, but distinctly shorter, than thorax; vertex plus frons more or less flattened; eyes large, holoptic, covering almost entire head; antenna shorter than head, scape subquadrate, slightly wider than long, pedicel much shorter, less than one half of scape length, more than twice wider than long, first flagellomere extremely swollen, nearly pyriform, much longer and wider than scape and pedicel combined, less than twice as long as wide, other flagellomeres gradually tapering apically, about three times as long as first flagellomere (Figs 1B, 2B).

Thorax subovate, mesoscutum longer than wide, slightly wider than head; scutellum small, rounded apically, distinctly wider than long; wing nearly three times as long as wide; C thickened but thinned just at wing tip; R1 slightly curved smoothly, about three-fourths of wing length; Rs arising from R more or less late, about at one-third of wing length; R2+3 parallel to R1, ending at C; “Pt” well developed, another brown marking between R1 and R2+3 below base of “Pt” present (Figs 1A, C, 2C); Rs stem shorter than bR4+5, bR4+5 shorter than dR4+5, fork of R4+5 clearly distad to level of fork of M1+2; r-m meeting anterior margin of discal cell basad to its midlength, bM1+2 about one half of dM1+2 length; br cell nearly as long as, but obviously narrower than, bm cell; discal cell nearly pentagonal, relatively short, about four times as long as wide; R4, R5, M1 and M2 slightly convergent, running towards wing tip (M1 ending just at wing tip); section of M3+4 slightly shorter than bM4; cell m3 nearly parallel quadrilateral but open apically; cell cu (traditionally anal cell) narrowly open. Legs with femora darkish brown, clavate, distinctly thicker than tibiae, tibiae and tarsi yellowish brown; femur of hindleg as long as, but twice as wide as, tibia, tibial spurs very short, distinctly less than tibial width, basitarsomere nearly as long as other tarsomeres combined, claw nearly as long as fifth tarsomere, empodium badly preserved, seemingly longer, but narrower, than pulvillus.

Abdomen ovate-oblong, with seven segments visible, clearly longer than head and thorax combined, with first segment longest, second segment widest, slightly wider than thorax; male genitalia longer than sixth segment with gonostylus (?) darkish brown, very narrow, strongly curved inwards.

Dimensions.

Holotype: length of body 10.9 mm; head, 1.4 mm; thorax, 3.6 mm; abdomen 6.4 mm. Length of wing 7.4 mm, width of wing 2.9 mm.

Remarks.

Sinonemestrius completus sp. n. differs from the type species Sinonemestrius tuanwangensis by the following features: R2+3 slightly curved, parallel to R1 and not meeting R1 end apically, fork of R4+5 distinctly distad to level of fork of M1+2, crossvein r-m meeting anterior margin of d cell basad to its midlength and wing membrane with a few markings (only limited to “Pt” and below it). On the other hand, this new species differs from Sinonemestrius akirai by Rs arising from R stem late (at about one-third of wing length vs near to wing base), the slightly curved R2+3 which runs parallel to R1 (vsR1 and R2+3 clearly convergent apically), fork of R4+5 distad (vs basad) to level of fork of M1+2 and cell m3 open (vs closed before hind margin of wing). Unfortunately, the body structures cannot be compared because the descriptions of the two known species are based on wing impressions.

Etymology.

Latin, completus (complete), referring to the species erected based on a complete fly.

Holotype.

No. NIGP L91803, a complete male fly, dorsoventral aspect, is held in the collection of NIGPAS.

Distribution.

Type locality and horizon: Laiyang Formation, in the vicinity of Tuanwang, Laiyang, Shandong, China (Lower Cretaceous).

Repository.

The Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences.