Ratites
Ratites are an informal grouping of flightless birds. At one time they were classified as an order however it is now known that the similarities between the families is a result of convergent evolution and not due to relatedness. The orders that make the ratites are Struioformes (ostrich), Rheiformes (Rheas), Casuariformes (Cassowaries and Emus). There are other orders of flightless bird such as the penguin and the kiwis however the ratites share the characteristic of not having a keel on their sternum.