Mo. Rev. Stat. § 509.460: Cross-claims against coparty.

A pleading may state as a cross-claim any claim by one party against a coparty arising out of the transaction or occurrence that is the subject matter either of the original action or of a counterclaim therein. Such cross-claim may include a claim that the party against whom it is asserted is or may be liable to the cross-claimant for all or part of a claim asserted in the action against the cross-claimant.