A short-horned cowfish with a single spine standing up from the middle of the back.
A cowfish to about 15 cm, sandy to olive-brown, the carapace patterned with wavy blue to blue-green lines and small pale spots. It has two short horns above the eyes and two short spines at the lower rear corners, and, the feature the name refers to, a single strong spine standing up from the middle of the back. Lactoria cornuta, which shares the same ground, grows to three times the size, has horns several times as long, and has no dorsal spine. Both are rigid-bodied and both hover rather than swim, so the spine and the horn length are what the identification rests on.
It works open sand, rubble and seagrass, feeding on small invertebrates exposed by blowing jets of water into the sediment, the same method as the longhorn cowfish and leaving the same small craters. The body is enclosed in fused bony plates and cannot flex, so all propulsion comes from the small fins and the fish moves slowly and deliberately.
Recorded from about 1 to 30 m. It is solitary, site-attached and unhurried, and generally drifts a metre or two and turns to keep an approaching diver in view rather than leaving.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.