Vestigial structure
Ria shotgun
vestigial An adjective for some existing structure (such as body part or organ) that over many, many generations seems to have lost any useful function. It may be much smaller than a functional organ in another species, or may be only partially developed.
Apr 05, 2006 · i don't know many who would consider the thymus a vestigial organ, it is true that the thymus, like tonsils, can be removed at a very early age but this is not a criteria for a vestigial organ, well not as far as i understand the definition of vestigial but maybe this was the definition in 1890. in lab mice the thymus can be removed 5 days after birth without any deleterious consequences ...