Okla. Stat. tit. 12, § 1143

It shall be sufficient in such action, if the defendant in his answer, deny, generally, the title alleged in the petition, or that he withholds the possession, as the case may be, but if he deny the title of the plaintiff, possession by the defendant shall be taken as admitted. Where he does not defend for the whole premises, the answer shall describe the particular part of which defense is made.