The caudal fin is deeply forked with its upper and lower caudal-fin lobes not bearing filaments.

There are 56 to 64 pored scales in the lateral line which is forked on the caudal fin, with branches reaching onto the rear margin of the lobes of the tail.

[1] The Atlantic threadfin occurs over sandy or muddy bottoms and on beaches, commonly being observed in the surf zone.

Young specimens, of lengths less than 66 millimetres (2.6 in) have been taken from the surface of the Gulf of Mexico where the sea was 1,035 to 2,736 metres (3,396 to 8,976 ft).

Spawning probably occurs in the Gulf of Mexico, off Louisiana and Texas and mainly takes place between mid-December and mid-March and lasts between 45 and 120 days overall.

[3] The Atlantic threadfin was originally formally described as Polynemus octonemus in 1858 by Charles Frédéric Girard with the type locality of Brazos Santiago, and Galveston, Texas.