vestigial

adj. of a vestige; of a remnant

In evolutionary biology and comparative anatomy, vestigiality is a term which describes homologous characters of organisms which have lost all or most of their original function in a species through evolution. These may take various forms such as anatomical structures, behaviors and biochemical pathways. Some of these disappear early in embryonic development, but others are retained in adulthood. All such characters can in turn can be traced to the genes which code for such characters. Some genes no longer code for anything, and can thus be said vestigial themselves, or junk DNA.
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Adjective
1. not fully developed in mature animals; "rudimentary wings"
(synonym) rudimentary
(similar) undeveloped
(classification) biology, biological science

adj. vestigial, of a vestige; of a remnant

adj. vestigial, of a vestige