Beastly Kingdom was the name of a "land" at Animal Kingdom that has yet to(and may never) materialize. Animal Kingdom was orignally intended to celebrate animals -- currently existing, extinct (hence, DinoLand), and imaginary. The hope was that Beastly Kingdom would help AK from seeming to be a zoo and would celebrate Disney imagination -- ideas thrown around included a dragon-type thrill ride (Dueling Dragons anyone?) and a scenic boat ride.
When bean-counters decided that AK needed cuts, Bestly Kingdom was shelved and a quick land like Camp Minnie/ Mickey was thrown together. Because of this, AK has a reputation for not being a full day park and the closest we may get to a BK is Expedition Everest.
JimHillMedia.com has a GREAT series of articles on Beastly Kingdom.