Knopphornfugl, Aceros cassidix "Sulawesi Red-knobbed Hornbill (aceros cassidix)" by Gregory Moine via Flickr, Creative Commons Attribution.

Rynkehornfugl, Aceros corrugatus "Wrinkled hornbill (Aceros corrugatus)" by Bob|P-&-S via Flickr, Creative Commons Attribution.

Detaljert systematikk:

Knopphornfugl, Aceros cassidix

U.art Aceros cassidix brevirostris (Legg til)

Rynkehornfugl, Aceros corrugatus

U.art Aceros corrugatus corrugatus (Legg til)
U.art Aceros corrugatus megistus (Legg til)
U.art Aceros corrugatus rugosus (Legg til)

U.art Aceros nipalensis nipalensis (Legg til)
U.art Aceros nipalensis yunnanensis (Legg til)