vestigial
/ve-ˈsti-jē-əl/
adjective
remaining in a form that is small or imperfectly developed and not able to function : being or having the form of a vestige
remaining as the last small part of something that existed before
a vestigial tail
noun
a trace, mark, or visible sign left by something (such as an ancient city or a condition or practice) vanished or lost
the smallest quantity or trace
footprint