A new record of Pteragogus flagellifer (Valenciennes, 1839), Cocktail Wrasse (Actinopterygii, Perciformes, Labridae), from Taiwan, northwestern Pacific Ocean

Pteragogus flagellifer (Valenciennes, 1839), Cocktail Wrasse, is recorded from Taiwan based on a single specimen. Although this species has previously been recorded in Taiwanese literature, we found all the previous records to be based on misidentifications. Therefore, our specimen represents the first reliable record from Taiwan and fills the distribution gap of this species between the Philippines and Japan. A checklist of Pteragogus Peters, 1855 recorded from Taiwan is provided and discussed. A key to species of Pteragogus from the northwestern Pacific Ocean is also provided.