S.D. Codified Laws § 15-26A-76
The parties may allow to each other by stipulation, one extension of time not exceeding fifteen days for serving and filing the appellant's and appellee's initial brief, provided such stipulation is made and presented to the clerk of the Supreme Court before the time for filing such brief as provided in § 15-26A-75 has expired. Thereafter, no other extension of time fixed by these rules for filing briefs will be allowed, except upon application and notice. The application shall be made to the Chief Justice of the Supreme Court and shall be allowed only for good cause.
An extension of time for filing a brief in an adoption or an abuse and neglect action will be granted only upon application and notice, said application to be made to the Chief Justice of the Supreme Court and allowed only for good cause.
SDCL 15-26A-76