Trichonotus halstead, a new sand-diving fish from Papua New Guinea

Synopsis Trichonotus halstead, family Trichonotidae, is described from 3 males and 4 females collected from a sand slope off the northwest end of Normanby Island, Papua New Guinea. It was part of a large population of 4 sympatric species of Trichonotus. The elaborately colored dorsal fin of the male, distinct among trichonotids, is brilliant gold anteriorly followed by a black patch, then a series of 8 to 40 conspicuous, black or dark brown spots that extend onto the upper caudal fin. The spines of the long dorsal fin are filamentous in the male and are numerous (VI to VIII, VII) in both sexes. This species lives in harems (1 male: 4 or 5 females) in well-defined territories and spends more than 80% of its day perched on sand. It feeds on benthic crustaceans and low drifting plankton. When disturbed, it dives into the sand where it also spends the night. It retires within 18 minutes after sunset and emerges within 11 minutes of sunrise. Mating takes place 6:00 h on the sand and the female then picks up the eggs into her mouth. There is evidence of gill-chamber brooding.