Vestigial. (n.d.). In YourDictionary. Retrieved from https://www.yourdictionary.com/Vestigial
Relating to a body part that has become small and lost its use because of evolutionary change. Whales, for example, have small bones located in the muscles of their body walls that are vestigial bones of hips and hind limbs.
Heider bryonic membranes are vestigial or entirely wanting.
Tail vestigial or absent.
In some Psocidae the wings are in a vestigial state, and the fully winged species rarely if ever fly.
Maxillulae vestigial or absent.
The alimentary canal, which may be represented by a vestigial structure, is accordingly not functional, and the larva does not become pelagic. A pyriform organ is present in most Gymnolaemata as well as the sucker by which fixation is effected.