CIRCULATORY AND UROGENITAL VESTIGES “Other clear developmental ‘vestiges’ come from the circulatory system of eutherian (placental) mammals, which undergo rapid and radical changes from fetal to newborn circulation, and from vertebrate urogenital (excretory and reproductive) systems, which in both males and females share many incipient structures that quickly shift function during sexual differentiation.”
https://evolution-outreach.springeropen.com/articles/10.1186/s12052-014-0012-5