%gradatory%

a. [ See Grade. ] 1. Proceeding step by step, or by gradations; gradual. [ 1913 Webster ]

Could we have seen [ Macbeth's ] crimes darkening on their progress . . . could this gradatory apostasy have been shown us. A. Seward. [ 1913 Webster ]

2. (Zool.) Suitable for walking; -- said of the limbs of an animal when adapted for walking on land. [ 1913 Webster ]