During an ichthyofaunal survey of southern Japan, a single specimen (74.9 mm standard length; SL), collected at a depth of 8 m off Kashiwa-jima Island, Kochi Prefecture in June 1992, was found in the fish collection of the National Museum of Nature and Science, Tsukuba, Japan. The specimen was subsequently identified as a species of Thysanophyrys Ogilby, 1898, having the following combination of characters: dorsal surface of head lacking tubercles, suborbital ridge with six distinct spines (including one preorbital spine), lateral-line scales with two exterior openings posteriorly, ocular papillae absent, interopercular flap absent, and well developed sensory tubes on upper cheek region. The specific identification as T. randalli Knapp, 2013 was based on the short snout (length 10.1% of SL), a single preocular spine, no supraocular tentacles, the iris lappet without branches, interopercle expanded posteroventrally, and six scale rows between the second dorsal-fin origin and lateral line. Thysanophyrys randalli having been recorded previously only from the western Indian Ocean and Pacific Ocean north to Kiribati, the Kochi specimen represents the first northwestern Pacific (including Japanese waters) and northernmost records of the species. The species is compared in detail with the closely related congener Thysanophyrys chiltonae Schultz, 1966. In Japanese waters, both species occur around the southern oceanic islands. The new standard Japanese name “Kokuchikuroshimagochi” is proposed for T. randalli (“Kuroshimagochi” applied to T. chiltonae).
