Types of Caudal fin

(A) – Heterocercal,

• The heterocercal tail is sometimes called the shark-tail type of caudal fin. Elasmobranch (cartilaginous fish) and some primitive type of bony fishes contain this type of fin.
• This fin has two unequal lobes where the upper smaller lobe is known as epichordal lobe and a much larger lower lobe is known as hypochordal lobe.
• In this case, the hind end of the vertebral column becomes bent upwards and continues almost up to the tip of the fin.

(B) – Protocercal,

• It is the most primitive type of caudal fin where the straight vertebral column divides the caudal fin into two equal lobes such as upper lobe and lower lobe.
• In this case, the upper lobe is known as epichordal or epicaudal and the lower lobe is called hypochordal or hypocaudal lobe.
• A series of rods are arranged around the central axis of the caudal region, which support the fin membrane.
• Undoubtedly, during the developmental period, the caudal fin of all fishes passes through the protocercal stage. This type of fin is found in cyclostomes and the living dipnoans(lungfishes).

(C) – Homocercal,

• Most of the higher teleosts have homocercal caudal fin.
• It has superficially symmetrical and two equal sized lobes such as upper epichordal and the lower hypochordal lobe.
• Internally, this tail is asymmetrical and the hinder end part of the vertebral column is greatly shortened and turned upward.
• In this case, the vertebral column does not touch the posterior limit of the fin.

(D) – Diphycercal

• Sharks possess a heterocercal caudal fin.
• The dorsal portion is usually larger than the ventral portion
• The high-performance bigeye tuna is equipped with a homocercal caudal fin and finlets and keels.