How to Identify Unicorn Leatherjacket

To identify Unicorn Leatherjacket (Aluterus monoceros), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

Typically grey to brownish-grey, often with irregular darker spots or blotches. Can change coloration to blend with surroundings. Fins are generally translucent.

Scale type

none

Mouth position

terminal

Distinctive features

A single, prominent, erectile spine (the 'horn') located just above the eyes, anterior to the soft dorsal fin., Small, rough, sandpaper-like scales (setae) giving it a leathery texture., Small, terminal mouth with strong teeth., Deeply forked caudal fin in adults.

Dorsal fin

Two dorsal fins; the first consists of a single, strong, erectile spine, followed by a very small, rudimentary second spine (often embedded and not visible), and the second dorsal fin is long and soft-rayed (46-50 rays).

Tail fin

Deeply forked in adults, becoming more rounded in juveniles.

Pectoral fin

Small and rounded (13-15 rays).

Distinctive fins

Pelvic fin is absent, replaced by a dewlap-like structure or a small, immovable spine.

Identification Tips

1. 1

   Dorsal Spine

   Look for the single, prominent, erectile spine on the head, resembling a 'horn'. This is the most distinguishing feature.

2. 2

   Caudal Fin

   Adults have a distinctly forked tail fin, unlike many other filefish species which have rounded or truncate tails.

3. 3

   Body Shape

   Elongated and highly compressed body, giving it a thin, disc-like appearance when viewed head-on.

4. 4

   Coloration

   Generally drab grey to brown, often with subtle mottling or spots, allowing for camouflage.

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