On July 10, 2012, approximately 1245 central daylight time, a Cessna 172M, N12504, registered to a private individual, sustained substantial damage while landing in a field after a loss of engine power near South Wayne, Wisconsin. The airline transport rated pilot sustained minor injuries, and one passenger was not injured. Visual meteorological conditions prevailed and a flight plan was not filed for the personal cross country flight being conducted under the provisions of Code of Federal Regulations Part 91. The flight originated at 1230 from Kokomo, Indiana, and was enroute to St. Paul, Minnesota (SGS).The passenger had just purchased the airplane in Kokomo, Indiana, and the intent of the flight was to return the airplane to his home base in St. Paul, Minnesota. After 2 hours and 20 minutes of uneventful flight, cruising at 4,500 feet msl, the engine RPM decreased. The pilot applied carburetor heat and about 2 minutes later, the engine RPM decreased to about 1500 RPMs, the oil pressure dropped to zero, and the propeller stopped. The oil temperature indicator in the cockpit was in the normal range. The pilot elected to execute a forced landing in a soy bean field since an airport was not within glide distance. Upon touchdown in the field, the airplane flipped inverted which resulted in substantial damage to the empennage and left wing. Both occupants exited the airplane and were transported to the hospital. The pilot stated that he had back pain. The airplane wreckage was evaluated by FAA inspectors who traveled to the accident site. A sufficient quantity of oil (about 5 quarts) was present in the engine. The lubrication system appeared to be intact and in compliance with applicable airworthiness directives. There were connecting rod failures which appeared to have resulted from oil starvation. Further examination revealed two pieces of foreign plastic-like material lodged in the oil sump screen. The two pieces dimensions' were approximately 1/4 inches x 3/8 inches, and 1/4 inches x 5/16 inches, respectively.