Apidium phiomense is the most common primate from the early Oligocene deposits of Fayum, Egypt. It is known from hundreds of dental remains and dozens of skeletal remains, including numerous representatives of the long bones of the forelimb and hindlimb. Apidium phiomense was a small (1,600 g) arboreal quadruped. The forelimb bones of this species show features characteristic of arboreal quadrupeds and lack characteristic features found in the forelimb bones of vertial clingers, terrestrial quadrupeds, or suspensory species. The pelvis and hindlimb bones show numerous adaptations for leaping from a quadrupedal position. In general, Apidium lacks characteristic features of either cercopithecoid monkeys or hominoid apes. Overall, the skeleton shows greatest similarities to the same elements of small platyrrhines such as Saimiri and is also very similar to the hypothetical morphotype for ancestral platyrrhine. The skeleton of Apidium phiomense is the most primitive anthropoid postcranial skeleton known.