Vestigial structures take many forms: organs, behaviors, and even biochemical processes. Their defining characteristic is they are structures that a species has retained, but no longer serve their ...

Megachirella, the mother-of-all-lizards (and snakes). Davide Bonadonna/Nature . Around 252 ... as well as bones that survive today in modern lizards as reduced vestigial structures. ...

The Oxford English Dictionary (OED) defines vestigial organs as organs or structures remaining or surviving in a degenerate, atrophied, or imperfect condition or form.