Distinctive Characters: Dorsal fin with 8 spines and 13 rays. Anal fin with 3 spines and 11 rays. Pectoral fin with 15 rays. Body depth 3.8-4.2 in standard length. - No scales dorsally on opercle. Caudal fin truncate to slightly emarginate, becoming lunate in large males.
Colour: Initial phase with broad black stripe through eye to upper caudal. Green above, cream below. Caudal margins broadly orange. Terminal males purplish. Head blue. Nape yellow. Two fine oblique gold lines on cheek.
Habitat and Biology: Occurs in small aggregations over shallow reefs to depths of 15 m. Feeds on zooplankton well above the substrate.
Remarks: T. melanochir (Bleeker) is a synonym based on the terminal male of Thalassoma amblycephalum. Initial phase fish far more numerous than terminal males.