From Cheng and Thompson (2008):
"Ceratophya is a distinct subgroup of Microdon restricted to the neotropics. Ceratophya has had a confused history. Wiedemann (1824: 14) erected the group for two species similar to Microdon but differing by having a more slender habitus, much longer basoflagellomere and simple scutellum without calar. He described two species, notata and longicornis, of which notata was figured. Subsequently notata was selected as the type of the genus (Blanchard 1846: 145, also Coquillett 1910: 520, Curran 1941: 253). Macquart (1834: 488) recognized the genus following Wiedemann's characters and described a new species (fuscipennis, now Microdon (Microdon)) from Philadelphia. Later Walker described three additional species (variegata Walker 1852: 220, now Paramixogaster; bicolor 1857: 79, now Microdon (Microdon), and luridescens Walker 1857: 151, now Microdon (Microdon)). Williston (1886: 310, 1887: 4) did not recognize the genus as he felt it was based on the lack of scutellar calcars, which he considered a trivial character. Kertész (1910: 360) cataloged the genus as valid and included five species. Subsequent authors followed Williston until Curran (1941: 247, 253) resurrected the genus. Curran without explanation recognized the group as having no appendix on vein R4+5 and included a diverse group of species in his Ceratophya (notata Wiedemann = type; longicornis Wiedemann = Ceratophya, goettei Shannon = Ubristes (Ubristes), flukei Curran = Paramicrodon, bicolor Walker = Microdon (Microdon), plaumanni Curran = Ubristes (Ubristes), analis Curran = Ubristes (Ubristes) and macroptera Curran = Aristosyrphus (Aristosyrphus)). Due to his error in placing Ceratophya as a genus without an appendix, subsequent workers mis-identified the genus. Hence, the genus does not properly key out in Hull world key (1949: 306), so this name was mis-identified by Keiser and others. The Malagasy species previously assigned to Ceratophya were placed into the genus Afromicrodon. The presence or absence of an appendix on vein R4+5 has obviously been critical in the placement of this name. In the original figure this appendix shows as running from vein R4+5 to vein M, but later (Wiedemann 1830, pl. 9, fig. 5; our figure 49) this was corrected to on the left side to show an appendix clearly separated from vein M, but on the right side without any appendix. Could this have been the basis of Curran's error, that is, looking only at the right side?
Thompson have examined the type of Ceratophya notata Wiedemann and find that it corresponds well to Wiedemann's original figure, but the appendix on vein R4+5 while long does not end in vein M. The species is also structurally similar to Microdon panamensis Curran."