Answer:
This would be an example of a vestigial structure.
Explanation:
Vestigial structures or organs are are an anatomical feature or even a behavior that has remained even though it no longer has any true utility or purpose in that organism's current form. For us humans, for instance, the appendix and the wisdom teeth are known vestigial structures. The pelvic girdle is most likely a vestigial structure when it comes to whales. Their pelvic bones are too small when compared to the whales' bodies, which led scientists to believe they are remnants from an ancestor that once walked on land.