Perhaps the largest sample of Miocene ape fossils, dated over the longest time period, is Proconsul. Extending from over 22 million years ago to around 10 million years ago across East Africa, the fossil record of this genus consists of over a thousand skeletal elements, representing much of its anatomy.
Unlike living apes, Proconsul was a quadruped, with several features reflecting this adaptation, including:
- forelimbs and hindlimbs of the same approximate length
- the lower part of the spine is long and flexible for quadrupedal movement
- the hands were used for palm-down walking as in living monkeys
Some scientists believe that Proconsul may have had a tail, based on the evidence for tendon attachments on the sacrum, although other scientists disagree and no tail bones have been found. There appear to have been at least three species of Proconsul, though the level of sexual dimorphism was high in each, making it difficult to separate within-species and between-species variation. The species varied in body size, ranging from a small form at 15 to 20 kg to a large form that approached 50 kg. The molar teeth of all species had thin enamel and low cusps, which may reflect a diet concentrating on fruits. As in Aegyptopithecus and other early catarrhines, the molars had an extensive cingulum.
It is possible that all later apes share a Proconsul-like ancestor, with the development of vertical body posture and suspensory locomotion that distinguish later hominoids. But it is not out of the question that the Proconsul lineage is a much more distant relative to living apes, perhaps even representing an extinct catarrhine superfamily separate from hominoids and cercopithecoids. The position of Proconsul in the hominoid phylogeny is potentially important because of its implications for the evolutionary relationships of later apes. If later apes evolved from a Proconsul-like form rather than a gibbon-like brachiator, for example, then their locomotor evolution may have followed a substantially different path.