[2] An unrelated species sometimes known by the name threadfin, Alectis indicus, is properly the Indian threadfish (family Carangidae).

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.

In some species, such as the royal threadfin (Pentanemus quinquarius), the thread-like rays may extend well past the tail fin.

Threadfins frequent open, shallow water in areas with muddy, sandy, or silty bottoms; they are rarely seen at reefs.

Presumed to be pelagic spawners, threadfins probably release many tiny, buoyant eggs into the water column, which then become part of the plankton.