A homocercal tail is a caudal fin composed of two lobes of equal proportion. Homocercal tails are the most common caudal fin type in fish but can come in many symmetrical shapes. A homocercal tail is contrasted with a heterocercal tail which has unequal lobes.
A heterocercal tail is a caudal fin composed of two asymmetrical lobes. Often, such as the case in many sharks, the vertebral column passes through the upper lobe, making it the larger of the two lobes. A heterocercal tail is contrasted with a homocercal tail which has equal lobes.