Final answer:
Ardipithecus ramidus was discovered by Tim White in Ethiopia in 1992. It is the first hominin species dated to the Pliocene era and displays bipedal characteristics.
Step-by-step explanation:
The discovery of Ardipithecus ramidus was made by American paleoanthropologist Tim White in Ethiopia in 1992. Ardipithecus ramidus is the first hominin species to be dated to the Pliocene era, about 4.4 million years ago. The fossil evidence suggests that Ardipithecus was bipedal and lived in both heavily forested environments and on the ground. The reduced canine in Ardipithecus is a derived trait that appeared earlier than A. ramidus and is believed to be a result of decreased aggression and female preference for males with milder temperaments.