Orrorin tugenensis is an early hominin estimated to be about 6 million years old, living near the time our oldest hominid ancestor split from the great apes. Evidence indicates that O. tugenensis was likely bipedal. Its teeth suggest it could be more closely related to Homo sapiens than Australopithecus species, though this relationship remains highly speculative.

Arizona State University

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An unclassified genus is usually a result of limited to scarce information or artificats found to identfy a specific genus:

Unclassified Genus 

Ar. ramidus is considered by some to be the oldest-known hominid. Ar. ramidus shares some novel characteristics with later hominids, including being bipedal and its teeth. As the molars of Ar. ramidus are smaller than those of any of the Australopithecus species. Further evidence, indicates that it may have been a woodland forest dweller. 

(Note: This species has not yet been fully described because some of the specimens have been difficult to extract from the surrounding rock.)

Ardipithecus Ramidus 

Although Kenyanthropus platyops occupied parts of Africa at the same time as A. Afarensis, K. platyops is distinctive physically. The features that distinguish K. platyops from A. Afarensis, include small ear holes, a relatively flat face, and small molars. Some scientists have placed H. rudolfensis specimens in the genus Kenyanthropus. Others ignore Kenyanthropus as a genus altogether, placing K. platyops specimens into the genus Australopithecus, saying that the species is not different enough to warrant its own genus. 

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