Concept
Version 13
Created by Boundless
Vestigial Structures

Whale Skeleton
The pelvic bones in whales are also a good example of vestigial evolution (whales evolved from four-legged land mammals and secondarily lost their hind legs). Letter c in the picture indicates the undeveloped hind legs of a baleen whale.
Source
Boundless vets and curates high-quality, openly licensed content from around the Internet. This particular resource used the following sources:
"Whale Skeleton."
https://commons.wikimedia.org/wiki/File:Whale_skeleton.png
Wikipedia
Public domain.