High Quality Content by WIKIPEDIA articles! This is a list of the Families, Species and Sub-species belonging to the Procellariiformes Order. However, there is scientific disagreement regarding this order, in particular, the Procellariidae family. BirdLife International has subscribed to the newer way of thinking, whereas, James Clements in his The Clements Checklist of Birds of the World is still waiting. This list shows both the new and old versions.