Anatomy
H
Heterocercal Tail
/ /ˌhɛtərəˈsɜːk(ə)l/ /
Etymology:
From Greek heteros (different) + kerkos (tail)
Quick Definition
An asymmetrical tail in which the vertebral column curves upward into the enlarged upper lobe, as in sharks.
📖 Full Definition
In a heterocercal tail the vertebral column bends upward into the dorsal (epichordal) lobe of the caudal fin, making the upper lobe larger. This is the ancestral condition for fishes and is retained in sharks, rays, sturgeons, and gars. The heterocercal tail produces a lift component when the fish swims, counteracting the tendency of a dense, non-buoyant fish to sink. In sharks, this is supplemented by the pectoral fins acting as aerofoils.
💡 Examples & Context
The enormous upper lobe of a thresher shark's caudal fin — up to half the body length — is used to herd and stun prey.