Pleadings

1. "How presented. — Every defense, in law or fact, to a claim for relief in any pleading, whether a claim, counterclaim, cross-claim, or third-party claim, shall be asserted in the responsive pleading thereto if one is required, except that the following defenses may at the option of the pleader be made by motion:
2. lack of jurisdiction over the subject matter,
3. lack of jurisdiction over the person,
4. improper venue,
5. insufficiency of process,
6. insufficiency of service of process,
7. failure to state a claim upon which relief can be granted,
8. failure to join a party under Rule 19. A motion making any of these defenses shall be made before pleading if a further pleading is permitted. No defense or objection is waived by being joined with one or more other defenses or objections in a responsive pleading or motion. If a pleading sets forth a claim for relief to which the adverse party is not required to serve a responsive pleading, the adverse party may assert at the trial any defense in law or fact to that claim for relief. If, on a motion asserting the defense numbered (6) to dismiss for failure of the pleading to state a claim upon which relief can be granted, matters outside the pleading are presented to and not excluded by the court, the motion shall be treated as one for summary judgment and disposed of as provided in Rule 56, and all parties shall be given reasonable opportunity to present all material made pertinent to such a motion by Rule 56."

Note that the first sentence of Rule 12b requires that all defenses be pled in the answer.  Therefore, the statute of limitations must be pled in the answer or else it is waived.