Adapting to a cursorial lifestyle causes two inverse morphological changes to occur in the skeleto-muscular system: the pectoral apparatus used to power flight is paedorphically reduced while peramorphosis leads to enlargement of the pelvic girdle for running.[11] Repeated selection for cursorial traits across ratites suggests these adaptions comprise a more efficient use of energy in adulthood.[2] The name "ratite" comes from the Latin ratis, raft, a vessel with no keel.