While reviewing this group, Joseph (2002) discovered that an undescribed population existed in central Brazil (later also found in north-eastern Bolivia).

No diagnostic difference was found between the taxa amazonum and microtera; it was therefore recommend that the latter should be considered a junior synonym of the former.

Ribas et al. (2006) confirmed by mtDNA that P. amazonum should be considered a species separate from P. picta (otherwise, P. picta would be paraphyletic), but also showed that snethlageae was very close to, and arguably better considered a subspecies of, P. amazonum (as already had been expected due to a number of intermediate specimens suggesting that hybrids occur).

The nominate subspecies (P. a. amazonum) has a narrow blue forehead-band and pale grey scaling to the chest.

The remaining subspecies, P. a. snethlageae and P. a. lucida, have little or no blue to the forecrown and their chests are, uniquely for the P. picta complex, overall pale with relatively narrow, dark pointed markings.