Systematics

Monotypic.

Type specimen (as Cultrides rufipennis) from lower Orinoco River, Venezuela described by Gray (1849).

Gray (1849) noted that the Rufous-winged Ground-Cuckoo was “supposed to be native of Mexico” but this later was corrected by Chapman (1928).

A single male specimen collected at Mt. Duida, Venezuela in 1913 was described by Chapman (1914) as Neomorphus nigrogularis, a new species closely related to the Rufous-winged Ground-Cuckoo. Chapman commented at the time that the differences in plumage between these "species" could possibly be attributed to the Duida specimen being an immature. However the collector, L.E. Miller, noted that the specimen had enlarged testes and, thus, was at least sexually mature. Chapman later downgraded nigrogularis to a subspecies of rufipennis Chapman (1928), with nigrogularis occurring in Guyana and the upper Orinoco, and nominate rufigularis restricted to the lower Orinoco only. N. nigrogularis is now considered synonymous with N. rufipennis (Phelps and Phelps 1958, Payne 2005, Erritzöe et al. 2012).

Rufous-winged Ground-Cuckoo is one of five species (but see below) that comprise the genus Neomorphus (meaning "new form"). Neomorphus is classified in the cuculid subfamily Neomorphinae, which contains five genera of terrestrial New World cuckoos. Neomorphus is thought to be most closely related to cuckoos of the genus Geococcyx, which includes the Greater (G. californianus) and Lesser (G. velox) roadrunners of North and Central America. The other members of the Neomorphinae are Morococcyx, a smaller non brood-parasitic species, and three obligate brood parasitic species of the genera Tapera and Dromococcyx, which occur in Central and South America. Sorenson and Payne (2005) consider Morococcyx to be the sister taxon to the Neomorphus-Geococcyx clade, with the parasitic Tapera-Dromococcyx clade as basal sister group to the non-parasitic Neomorphus-Geococcyx-Morococcyx assemblage.

There was much debate in the mid-19^th century regarding the species status of Rufous-winged Ground-Cuckoo. Some naturalists believed that it was a subspecies of Red-billed Ground-Cuckoo (N. pucheranii); another suggested, based on the examination of only a single specimen, that it was the immature of Rufous-vented Ground-Cuckoo (N. geoffroyi) and concluded that Rufous-winged, Red-billed, and Rufous-vented ground-cuckoos were all the same species. This debate was resolved by Lawrence (1873) who separated the three taxa into valid species. See Lawrence (1873) for more details on this controversy.

Haffer (1977) allied Rufous-winged Ground-Cuckoo with Red-billed Ground-Cuckoo, and classified them in a superspecies, on the basis of similarities in their plumage, such as their uniform blue black upperhead, apically marginated (V-shaped) gray or clay colored lateral breast feathers (not semicircularly marginated as in Banded Ground-Cuckoo N. radiolosus and Rufous-vented Ground-Cuckoo), and presence of red orbital skin. This association is supported by Sorenson and Payne (2005) based on mitochondrial DNA evidence.

Both Haffer (1977) and Payne (2005) recognized only four Neomorphus species because they considered Scaled Ground-Cuckoo (N. squamiger) to be a subspecies of Rufous-vented Ground-Cuckoo. A more recent studym however, has suggested that Scaled Ground-Cuckoo should be treated as a species due to differences in mitochondrial DNA and face, neck, and breast plumage between Scaled and Rufous-vented ground-cuckoos (Firme et al. 2014).