Pliopithecus antiquus was among the first fossil primates ever unearthed. Discovered by Édouard Lartet in 1837 in Sansan, France, the original specimen was named by Henri-Marie Blainville in 1839, but was not officially nominated as a taxon until 1849 by Paul Gervais.
Among pliopithecoids, P. antiquus is one of the most complete specimens. The type specimen consists of a nearly complete mandible with missing rami. All of the lower teeth are present, with only the crowns missing from the right canine and left second incisor. P. antiquus remains one of the smallest pliopithecoids discovered, its small dental size being among its most identifying features.
P. antiquus was a widespread species known from multiple sites in France as well as sites in Germany, Poland, and Switzerland. Based on biostratigraphy, P. antiquus is known primarily from fossil strata assigned to MN6 (15 million years ago), but t has been suggested that P. antiquus may have persisted to MN9 (11 million years ago).