In the absence of valid testamentary disposition, the undisposed property of the deceased devolves by operation of law in favor of his descendants, ascendants, and collaterals, by blood or by adoption, and in favor of his spouse not judicially separated from him, in the order provided in and according to the following articles.

           Acts 1981, No. 919, §1, eff. Jan. 1, 1982.