Ringtail Unicornfish (species: Naso annulatus) in Lizard Island Field Guide (Lizard Island Field Guide)
Naso annulatus
Ringtail Unicornfish

©Andy Lewis: Young Naso annulatus at the lagoon entrance, Lizard Island.
Kingdom Animalia
Phylum Chordata
Class Actinopterygii
Order Perciformes
Family Acanthuridae
Genus Naso
Species Naso annulatus



Distinguishing features

Long tapering horn develops on forehead with size, starting when fish is about 20 cm long. No markings on head. Young with a white ring around tail peduncle. Adults develop long, trailing filaments on tail. Colour often olive/brown but can change rapidly to much paler blue/grey.


  • From 2 cm to 100 cm (Length of specimen)

Depth range

  • Depth range data is not yet available.


Similar taxa


©Atlas of Living Australia: Australian distribution

Web resources


References that assist with identification

  • Allen and M.V. Erdmann, G.R. (2012). Reef fishes of the East Indies. Volumes I-III in: Reef fishes of the East Indies. Tropical Reef Research, Perth, Australia. LIRS catalog number 90162.

Other references

  • Borden, W.C. (1998). Phylogeny of the unicornfishes (Naso, Acanthuridae) based on soft anatomy, Copeia, 1998(1): 104-113. LIRS catalog number 528.
  • Caley, M.J. (1991). Mechanisms of coexistence in communities of coral-reef fishes, Ph.D. thesis, University of Sydney. LIRS catalog number 307.
  • View all references