Pycraft (1900) presented a major advance when he coined the term Palaeognathae. He rejected the Ratitae-Carinatae classification that separated tinamous and ratites. He reasoned that a keelless, or "ratite", sternum could easily evolve in unrelated birds that independently became flightless. He also recognized that the ratites were secondarily flightless. His subdivisions were based on the characters of the palatal skeleton and other organ systems. He established seven roughly modern orders of living and fossil paleognaths (Casuarii, Struthiones, Rheae, Dinornithes, Aepyornithes, Apteryges, and Crypturi – the latter his term for tinamous, after the Tinamou genus "Crypturellus").