Oreopithecus bambolii is known from a series of well-preserved fossils, including some relatively complete skeletons, from the north of Italy dated to between 7 and 9 million years ago. This date makes the fossils much later than Proconsul, Afropithecus, and other early hominoids, but its relationships may be closer to these ancient lineages than to other apes dating to the past ten million years. </p>
Oreopithecus fossils come from a region that was an island during the Late Miocene, so the population may have been isolated for some period of time during its evolution. The teeth of Oreopithecus make it morphologically unlike most other hominoids. The upper incisors are relatively large and rounded, but the lateral upper incisors are small, peg-like teeth. Both upper and lower molars are high-cusped teeth for shearing plant matter, with an extra cusp on the lower molars. The unique characteristics and primitive dentition make it difficult to determine the exact relationships of Oreopithecus with other fossil hominoids around its age, which are known almost exclusively from their teeth. </p>
What is most interesting about Oreopithecus is the extensive preservation of its postcrania. At around 30 kg, Oreopithecus shows evidence for below-branch suspensory locomotion, including a relatively short trunk and hindlimbs and long forelimbs. Joint mobility was high, and the elbow joint was like that of living apes (Fleagle, 1988). Together, these details tend to indicate an adaptation much like living apes, in a form slightly smaller than chimpanzees.
On the other hand, some details have prompted some scientists to suggest hominid-like resemblances for Oreopithecus. The pelvic bones may indicate a more vertical habitual posture for Oreopithecus than in other apes (Rook et al., 1999), perhaps indicating a greater use of bipedal posture for above-branch walking. Evidence from the hand and wrist may indicate greater manual dexterity than in living apes, another possible hominid resemblance (Moya-Sola, 1999). These resemblances may not indicate a close relationship, but they certainly point to the diversity of adaptations of the Miocene apes among the great number of different lineages that existed.