Ringtail Unicornfish, Naso annulatus (Quoy & Gaimard, 1825)

Scientific name: Naso annulatus
Alternative name/s:
Short-horned Unicorn-fish, White-margin Unicorn
  • Author(s)
    Mark McGrouther
  • Updated
    15/02/22
  • Read time
    2 minutes
Ringtail Unicornfish, <i>Naso annulatus</i> Click to enlarge image
A 78cm long Ringtail Unicornfish speared by A. Boomer at a depth of 15m, Wreck Island, off Gladstone, Queensland, December 2002 (AMS I.42675-001). Image: Carl Bento
© Australian Museum

Fast Facts

  • Classification
    Genus
    Naso
    Species
    annulatus
    Family
    Acanthuridae
    Order
    Perciformes
    Class
    Actinopterygii
    Subphylum
    Vertebrata
    Phylum
    Chordata
    Kingdom
    Animalia
  • Size Range
    The species grows to 1 m in length.

Introduction

When the Ringtail Unicornfish is about 20 cm in length a long horn develops from a bump anterior to the eye. The species occurs in tropical marine waters of the Indo-Pacific.

Identification

The body of the Ringtail Unicornfish tapers to a narrow caudal peduncle. There are two scutes on the caudal peduncle, each bearing a strong keel. When fish are about 20 cm in length a long horn develops from a bump anterior to the eye. The horn of mature fish can be as long as the head. The species is brown to grey or blackish. Juveniles often have a white ring around the caudal peduncle. The caudal fin margin and membranes of adults are white.

Ringtail Unicornfish, Naso annulatus
Ringtail Unicornfish, Naso annulatus
Ringtail Unicornfish, Naso annulatus

Habitat

Juveniles can be found on reefs around shallow lagoons. Adults are usually seen in small schools at depths over 20 m on reef dropoffs.

Distribution

It occurs in tropical marine waters of the Indo-Pacific. In Australia this species is known from the offshore islands of north-western Western Australia, the entire length of the Great Barrier Reef, Queensland and Lord Howe Island.

The map below shows the Australian distribution of the species based on public sightings and specimens in Australian Museums. Click on the map for detailed information. Source: Atlas of Living Australia.

Distribution data sourced from the Atlas of Living Australia

References

  1. Allen, G.R. 1997. Marine Fishes of Tropical Australia and South-east Asia. Western Australian Museum. Pp. 292.
  2. Hoese, D.F., Bray, D.J., Paxton, J.R. & G.R. Allen. 2006. Fishes. In Beesley, P.L. & A. Wells. (eds) Zoological Catalogue of Australia. Volume 35. ABRS & CSIRO Publishing: Australia. parts 1-3, pages 1-2178.
  3. Kuiter, R.H. & H. Debelius. 2001. Surgeonfishes, Rabbitfishes and their relatives. A Comprehensive Guide to Acanthuroidei. TMC Publishing. Pp. 208.
  4. Myers, R.F. 1999. Micronesian Reef Fishes. Coral Graphics. Pp. 330.
  5. Randall, J.E., Allen, G.R. & R.C. Steene. 1997. Fishes of the Great Barrier Reef and Coral Sea. Crawford House Press. Pp. 557.