Complex sentence: The Oklahoma City Yard Dawgz are a member of the new Arena Football League which started play as a 2004 expansion team of the original Arena Football League's now-defunct minor league af2.
Split into simpler sentences: The Oklahoma City Yard Dawgz is a member of the new Arena Football League. The team began play as a 2004 expansion team of the original Arena Football League's now-defunct minor league af2.