homocercal tail

A homocercal tail is a type of fish tail fin where the upper and lower lobes are approximately symmetrical. The vertebral column ends near the middle of the tail's base. This tail structure is a key characteristic of teleosts, which are the most advanced group of bony fishes and include most commercially important fish species.12

The development of the homocercal tail was a significant evolutionary advancement, contributing to improved swimming efficiency compared to earlier tail types like the heterocercal tail found in some primitive fishes. This efficient tail, along with other adaptations, allowed teleosts to become the dominant fish group, inhabiting diverse environments from deep oceans to freshwater streams.32