[4] The International Ornithological Committee (IOC), the Clements taxonomy, and the South American Classification Committee of the American Ornithological Society (SACC) recognize two subspecies of lettered aracari: the nominate P. i. inscriptus (Swainson, 1822) and P. i. humboldti (Wagler, 1827).

BirdLife International's Handbook of the Birds of the World treats it as a species, "Humboldt's araçari".

[8] Nominate males have a black head except for bare blue, violet gray, and red skin around the eye.

Their breast, belly, and undertail coverts are yellow with pale buff cinnamon blotches.

[8] Both sexes of subspecies P. i. humboldti have plumage very like the nominates' except for cinnamon or rufous tibial feathers.

)[8] The species inhabits a variety of lowland evergreen forest types in the upper Amazon basin.

[8] The lettered aracari's nesting season appears to span from December to July in the western part of its range and from August to March in eastern Brazil.

[8] The IUCN follows HBW taxonomy and so has assessed the two subspecies of lettered aracari as separate species.

It is "reliant on forested habitats, and so, although it tolerates advanced second growth, it is vulnerable in the long term to Amazonian deforestation.