S.D. Codified Laws § 1-32-12
Any employee who was a member of any retirement system before the transfer of any board, commission, department, division, or agency specified by chapters 1-32 to 1-47, inclusive, shall not lose any retirement benefits accrued in such system by virtue of such transfer. An employee so affected shall have the option of continuing as a member of the retirement system of which he was a member at the time of transfer or to join the retirement system to which the transfer makes him eligible. However, the affected employee shall make his election within six months from the date of the transfer. Unless otherwise provided in chapters 1-32 to 1-47, inclusive, each state officer or employee affected by the reorganization of the executive department of state government under said chapters is entitled to all rights which he possessed as a state officer or employee before such reorganization, including rights to tenure in office and rank or grade, rights to vacation and sick pay and leave, rights under any retirement or personnel plan or labor union contract, rights to compensatory time earned, and any other rights under law or administrative policy. This section is not intended to create any new rights for any state officer or employee but to continue only those rights in effect before any transfer or reorganization pursuant to chapters 1-32 to 1-47, inclusive.
SDCL 1-32-12