[2] Established by Edward Blyth in 1845 for the newly discovered ashy bulbul (H. flavala),[3] this genus contains four extant species.

But in this case, the closely related genera Alophoixus and Setornis would probably also have to be included, and as soon as the earliest described genus, Ixos, is merged with another its name would apply.

mtDNA NADH dehydrogenase subunits 2 and 3 and nDNA β-fibrinogen intron 7 sequence data puts it closer to (but still well distant from) the streaked bulbul (Ixos malaccensis).

But whether that species represents the core group of Ixos – around its type species I. virescens (Sunda bulbul or green-winged bulbul) –, or a distinct lineage worthy of separation in a new genus – in which case Hypsipetes might be merged into the core group of Ixos – has not been studied.

In any case, though minor, the Hemixos lineage with its stark white throat and light wing patches seems well distinct.