Final answer:
The fossils with the depicted traits found in East Africa dating back to 4.5 million years are most consistent with the species Ardipithecus ramidus, which is characterized by both bipedal and arboreal features.
Step-by-step explanation:
Based on the description given, the fossils found in a 4.5 million-year-old layer of earth in East Africa with low sexual dimorphism in canine size relative to apes, a pelvis intermediate in shape between humans and apes, an anterior foramen magnum, and a grasping big toe would most likely be from the species known as Ardipithecus ramidus.
Ardipithecus ramidus is recognized for its combination of bipedal locomotion and arboreal adaptations, such as a grasping big toe, which allowed it to be both bipedal on the ground and quadrupedal in the trees. Its teeth, including reduced canines and small jaws, distinguish it from the great apes and align with its classification as a hominin. The pelvis shape suggests bipedalism, while the position of the foramen magnum indicates an upright posture, falling into the heterogenous collection of traits represented in the species Ardipithecus ramidus.