Systematics

Currently Green Thorntail is classified as monotypic (Peters 1945, Dickinson 2003); earlier authors recognized a separate subspecies, aequatorialis (Berlepsch and Taczanowksi 1883), for populations in Central America (e.g. Ridgway 1911).

Described as Trochilus Conversii (Bourcier and Mulsant 1846); type locality Bogotá. The species name honors "M. Convers, a French naturalist resident in Bogotá, Colombia" (Wetmore 1968).

For much of its nomenclatural history, this species was classified in the genus Popelairia Reichenbach 1854 (e.g. Peters 1945, Wetmore 1968), but Popelairia now usually is included in Discosura Bonaparte 1850.

A recent phylogenetic survey of the phylogenetic relationships of hummingbirds, based on DNA sequence data from both mitochondrial and nuclear genes, reveals that hummingbirds (Trochilidae) constitute nine major clades, comprising the hermits, mangos, Patagona, topazes, coquettes, brilliants, mountain-gems, bees, and emeralds (McGuire et al. 2007, 2009). Discosura belongs to the coquette clade, and is sister to Lophornis. This analysis included only two species of Discusura, popelairii (Wire-crested Thorntail) and conversii, and so does not provide information on relationships within Discosura. Other genera in the coquette clade are Heliangelus, Sephanoides, Phlogophilus, Adelomyia, Aglaiocercus, Oreotrochilus, Opisthoprora, Ramphomicron, Lesbia, Chalcostigma, Oxypogon, Oreonympha, and Metallura (McGuire et al. 2007, 2009).