British Wildlife Wiki

The caudal fin is the tail fin, located at the end of the caudal peduncle.

The tail can be heterocercal, which means that the vertebrae extend into a larger lobe of the tail or that the tail is asymmetrical:

  • Epicercal means that the upper lobe is longer (as in sharks)
  • Hypocercal means that the lower lobe is longer (as in flying fish)
  • Protocercal means that the caudal fin extends around the vertebral column, present in embryonic fish and hagfish. This is not to be confused with a caudal fin that has fused with the dorsal and anal fins to form a contiguous fin.
  • Diphycercal refers to the special, three-lobed caudal fin of the coelacanth and lungfish where the vertebrae extend all the way to the end of the tail.
  • Most fish have a homocercal tail, where the vertebrae do not extend into a lobe and the fin is more or less symmetrical. This can be expressed in a variety of shapes.
    • The tail fin may be rounded at the end.
    • The tail fin may be truncated, or end in a more-or-less vertical edge (such as in salmon).
    • The fin may be forked, or end in two prongs.
    • The tail fin may be emarginate, or with a slight inward curve.
    • The tail fin may be lunate, or shaped like a crescent moon.