Final answer:
The specimen found in Ethiopia that suggests bipedalism and dates back to around 5.8-5.2 mya is Ardipithecus kadabba, which had a toe that indicates its ability to walk upright.
Step-by-step explanation:
The specimen found in Ethiopia dating around 5.8-5.2 million years ago (mya) that suggests bipedalism is Ardipithecus kadabba. It is one of the two species of the genus Ardipithecus identified, with Ardipithecus ramidus being the younger species. The toe of Ardipithecus indicates that it was probably capable of bipedal locomotion, and its fossil remains provide important evidence for the study of early human ancestors. Found in a heavily forested environment, Ardipithecus had features such as an opposable big toe, which suggested a combination of bipedalism on the ground and quadrupedalism in trees, reflecting a significant stage in human evolution.