Their bodies are elongated and fusiform, with spinous and soft dorsal fins widely separated. Their tail fins are large and deeply forked indicating speed and agility. The mouth is large and inferior a blunt snout projects far ahead. The jaws and palate possess bands of villiform (fibrous) teeth. Their most distinguishing feature is their pectoral fins: they are composed of two distinct sections, the lower of which consists of three to seven long, thread-like independent rays. Polynemus species may have up to 15 of these modified rays. In some species, such as the royal threadfin (Pentanemus quinquarius), the thread-like rays may extend well past the tail fin. This feature explains both the common name threadfin and the family name Polynemidae, from the Greek poly meaning "many" and nema meaning "filament". Similar species, such as the mullets (family Mugilidae) and milkfish (family Chanidae) can be easily distinguished from threadfins by their lack of filamentous pectoral rays.