Acmonorhynchus Oates, Avifauna B. I., ii, p. 381 (1890).
Type, Acmonorhynchus vincens Sclater.
This genus was created by Oates for the reception of a remarkable Flower-pecker confined to Ceylon which had previously been placed either in Prionochilus or Pachyglossa. It differs from both these genera in having only nine primaries. From Dicaeum it may be recognized by its very large short, thick bill, whilst from Piprisoma it differs in its rounded tail and the numerous hairs which cover the nostrils.
In Acmonorhynchus the sexes differ and the young bird resembles the female.