 Any number of further ranks can be used as long as they are clearly defined.The superorder rank is commonly used, with the ending -anae that was initiated by Armen Takhtajan's publications from 1966 onwards.The order as a distinct rank of biological classification having its own distinctive name (and not just called a "higher genus" "(genus summum))" was first introduced by the German botanist Augustus Quirinus Rivinus in his classification of plants that appeared in a series of treatises in the 1690s.