Features in their skeletons, namely the coracoid, humerus, tibiotarsus, and tarsometatarsus, that they share only with the Nestor parrots link them to that genus.

[3] The largest known fossil species of parrot, Heracles inexpectatus, was described in 2019 from bones also identified as early Miocene St Bathans fauna.

The generic epithet Heracles was named as an allusion to this genus, in one mythic tradition the Greek hero Herakles slew the king Neleus.

While it shares many skeletal similarities with the two previously mentioned species, N. daphneleeae is only tentatively classified as Nelepsittacus because of an inadequate representation of the tarsometatarsus.

N. daphneleeae was named in honor of geologist Daphne Lee for her contribution to the knowledge of Miocene terrestrial ecosystems in New Zealand.