Original: Two species are described in the literature: A. ramidus, which lived about 4.4 million years ago during the early Pliocene, and A. kadabba, dated to approximately 5.6 million years ago (late Miocene).
Simplified: Two species are known: A. kadabba, dated to about 5.6 million years ago (late Miocene), and A. ramidus, which lived about 4.4 million years ago during the early Pliocene.