Rule 205.4b

An object’s supertype is independent of its card type and subtype, even though some supertypes are closely identified with specific card types. Changing an object’s card types or subtypes won’t change its supertypes. Changing an object’s supertypes won’t change its card types or subtypes. When an object gains or loses a supertype, it retains any other supertypes it had. Example: An ability reads, “All lands are 1/1 creatures that are still lands.” If any of the affected lands were legendary, they are still legendary.