Mid 17th century. Originally from represent + -ive + -ly, although some (especially later) examples may rather represent transmission errors for representatively.
Definition of representively in US English:
representively
adverbˌrɛprɪˈzɛntɪvli
rare
Representatively.
Origin
Mid 17th century. Originally from represent + -ive + -ly, although some (especially later) examples may rather represent transmission errors for representatively.