Uniserial fin - a special plan of structure of pectoral and pelvic fins of keystepper and cartilaginous fishes, in which radial cartilages attached to basal cartilages are located only on one side.

There are 2 types of paired fins:

a) biserial type - fins have a central split axis to which the radials are attached in pairs (shovelnose and double-breathed fishes);

b) uniserial type - radials are only attached to one side of the central axis (Kysteptera fishes).

In kystepteran fishes, the radials are attached on only one side of a less well defined segmental central axis (uniserial type).