Final answer:
Orrorin tugenensis is the only preaustralopithecine found outside the East African Rift Valley. It is considered a hominin due to its bipedal traits, and its discovery in 2001 provides valuable insights into human evolution.
Step-by-step explanation:
The only preaustralopithecine found outside the East African Rift Valley is Orrorin tugenensis. Orrorin tugenensis was discovered in Kenya in 2001 and is estimated to be approximately 6 million years old. It is considered a hominin due to anatomical traits suggesting bipedalism, such as the enlarged femoral head and the teeth resembling those of modern humans. This species plays a significant role in understanding human evolution and its relationship to other ancestral hominins.