Prosyrphus, Grimaldi, 2018

Grimaldi, David A., 2018, Basal Cyclorrhapha In Amber From The Cretaceous And Tertiary (Insecta: Diptera), And Their Relationships: Brachycera In Cretaceous Amber Part Ix David A. Grimaldi, Bulletin of the American Museum of Natural History 2018 (423), pp. 1-97 : 1-97

Prosyrphus , new genus

DIAGNOSIS: (male only). Extensively holoptic; arista dorsal; mouthparts small, clypeus minute; scutum and scutellum with numerous scattered setulae, two pairs of prescutellar dorsocentral setae, notopleural setae, four pairs scutellar setae. Vein r-m at level of Sc apex; M with short apical fork, M 1 not connected to R 4+5; dm and cup cells very large; alula small; spurious vein and sc-r lacking; male abdominal segments 6–8 very asymmetrical, epandrium to left side, sternite 8 terminal and bulbous.

TYPE SPECIES: P. thompsoni , n. sp.

ETYMOLOGY: From Latin pro - (“first, before”), in reference to the stem-group position of the fossil among Syrphidae .

COMMENTS: Prosyrphus is a stem-group Syrphidae (fig. 51). It has a large cell bm (~⅓ length of wing), apex of CuA 1 incomplete (not reaching the wing margin), cell cup large, and male genitalia that are very asymmetrical with a bulbous, terminal sternite 8 (among other genitalic features). Based on the unique male, features of the frons (e.g., lack of macrosetae) cannot be determined. Moreover, the body is stout and short; wing shape broad and apically tapered, the body overall with few macrosetae, and the mesal surface of the pedicel has a tonguelike lobe inserted into the basal flagellomere, features consistent with many modern syrphids.

Prosyrphus lacks synapomorphies of crowngroup Syrphidae , namely: a large alula, sc-r and spurious veins, M 1 curved upward to meet R 4+5 preapically; M 2 lost (or at most a spur on the curvature of M 1). Kovalev (1979) reported a fragmentary specimen of a syrphid or syrphoid in Late Cretaceous Siberian amber, but the characters are too few for a definitive attribution, and it may no longer be available for study since many of the Siberian amber specimens at the Paleontological Institute in Moscow have disintegrated. Otherwise, Prosyrphus appears to be the most derived dipteran known from the Mesozoic, although I predict that syrphids more derived than Prosyrphus will eventually be found in the Late Cretaceous, especially in the Maastrichtian and Campanian.