Mont. Code Ann. § 70-29-208

Whenever it appears in an action for the partition of lands that one or more of the tenants in common, being the owner of an undivided interest in the tract of land sought to be partitioned, has sold to another person a specific tract by metes and bounds out of the common land and executed to the purchaser a deed of conveyance purporting to convey the whole title to the specific tract to the purchaser in fee and in severalty, the land described in the deed must be allotted and set apart in partition to the purchaser or the purchaser's heirs or assigns or in another manner that makes the deed effectual as a conveyance of the whole title to the segregated parcel if the tract or tracts of land can be allotted or set apart without material injury to the rights and interests of the other cotenants who may not have joined in the conveyance.