The membrane that covers the embryonic cloaca, formed by the union of proctodeal (anal pit) ectoderm and cloacal endoderm, with no intervening mesoderm; the urorectal septum joins the cloacal membrane and divides it into an anal membrane and a urogenital membrane; the point where the urorectal septum intersects the cloacal membrane is the future site of the perineal body; proliferation of mesoderm and ectoderm around the cloacal membrane produces primordial tissues of the external genitalia in both sexes: the genital tubercle, genital folds, and genital swellings. [ http://en.wikipedia.org/wiki/Cloacal_membrane ]