Mesochria fani Szadziewski and Szwedo

Szadziewski, Ryszard, Szwedo, Jacek, Sontag, Elżbieta & Wang, Bo, 2016, The oldest species of the relic extant genus Mesochria from Eocene Fushun amber of China (Diptera: Anisopodidae: Mycetobiinae), Palaeontologia Electronica (Amsterdam, Netherlands) 15 (8), pp. 1-11 : 4-5

Mesochria fani Szadziewski and Szwedo sp. nov.

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Etymology. The specific name is dedicated to Mr. Yong Fan, the director of the Fushun Amber Institute, in recognition of his important contribution to the study of Fushun amber.

Material examined. Holotype male, NIGP156988 , Fushun amber. Deposited in the collections of the Nanjing Institute of Geology and Palaeontology , Chinese Academy of Sciences , Nanjing, China. Specimen is slightly distorted and carbonized, due to preservation conditions of amber (Wu et al., 2000; Wang, X. et al., 2001), i.e., natural heating (autoclaving) in the deposit, which is often affecting amber inclusions from Fushun.

Diagnosis. The species is characteristic in having well-developed anal veins, the median fork much longer than the basal stem, the costal vein extending one third of the way between apices R 4+5 and M 1, and the mid leg with two tibial spurs. Fossil M. neotropica from Dominican amber differs in having the median fork slightly shorter than the basal stem, the costal vein ending halfway between R 4+5 and M 1, no anal veins, and the mid leg with one tibial spur. Both fossil species are much smaller than extant members of the genus.

Description. Male. Body dark, altered in amber, length 4.1 mm. Natural colours not preserved. Left mid leg separated from thorax more robust than unnaturally slender right leg ( Figure 2.1, 2.5 ). Distal flagellomeres missing, lost during preparation.

Head barely visible ( Figure 2.3 ). Eyes bare, very probably touching or narrowly separated. Ocelli on raised tubercle present. Antenna apparently with 14 more or less cylindrical flagellomeres. Proboscis ( Figure 2.3 .) short. Palpus 4-segmented, with distal three segments well visible. Fourth palpal segment cylindrical with evenly pointed apex, 4 times longer than third one ( Figure 2.3, 2.4 ).

Scutum barely preserved. Scutellum bearing 4 marginal bristles.

Wing typical of the genus ( Figure 2.2, 2.7 ): length measured from base 2.9 mm. Wing membrane hyaline. Costal vein distinctly extending one third of the way between apices R 4+5 and M 1. Subcostal vein bare, ending in C slightly proximal to base of radius. Radial sector Rs setose. Veins R 1 and R 2+3 convergent, contiguous apically. Median fork distinctly longer than basal stem (1.8 times). Cross veins complete. Two distinct anal veins present.

Fore and hind tibiae with single apical spur. Mid tibia with two apical spurs. Hind tibia with distinct tibial comb composed of dense row of setae. Claws small, equal, apices bifid; empodium absent. Measurements are given in Table 1.

Male genitalia barely visible ( Figure 2.5, 2.6 ). Gonocoxites large, fused. Cerci well developed, long.

Female unknown.

Age and occurrence. Early Eocene , Guchengzi Formation , Fushun amber. Xilutian coal mine, Fushun, Liaoning, China (41.8° N, 123.9° E; palaeocoordinates 43.5° N, 116.0° E) .

Figures

FIGURE 2. Holotype male of Mesochria fani Szadziewski and Szwedo, sp. nov. 1, habitus, lateral aspect; 2, wings; 3, mouthparts; 4, palpus; 5, legs; 6, wing reconstructed; 7, genitalia, lateral aspect.