Oreopithecus, a European ape at the center of yet another bipedal debate

During the Miocene (9–7mya)
the Italian peninsula, then reduced to a series of islands, was the jungle home to long-limbed apes like Oreopithecus (Figs. 1–3; Gervais 1872, 4 feet tall). This taxon has been at the focus of a bipedal/quadrupedal argument since the 1950s. (So have pterosaurs.) 

Huerzler 1949
considered this specimen, “the earliest known representative of the line that led to man.” The hand was capable of a precision grip, convergent with human ancestors. The relatively broad pelvis (Figs. 1–3) and short jaws with small canines and other teeth of Oreopithecus were once considered diagnostic for a place in the transition to human bipedality. 

Other workers have disputed this.
Oreopithecus was considered a jungle/swamp dweller with adaptations for hanging by its long arms from overhead branches. Gibbons have not yet been tested in the LRT, but the size and proportions appear similar.

While the hand and pelvis proportions
(Fig. 3) were similar to those of hominins (humans and their bipedal kin), the foot (Fig. 2, from another specimen) definitely was not. This indicates convergence, which remains rampant within the LRT.

Oreopithecus has not yet been added to the LRT.

Carbon isotopes
suggest a diet of “energy-rich underground tubers and corms, or even aquatic vegetation,” according to Nelson 2016. This is consistent with an arboreal yet swampy environment.

References
Gervais P 1872. Sur un singe fossile d’un espèce non ancore décrite, qui a été découvert au monte Bamboli. Comptes Rendues de l’Académie des Sciences Paris, 74: 1217-1223.
Harrison T 1990. The implications of Oreopithecus for the origins of bipedalism, in Coppens, Y; Senut, B, Origine(s) de la Bipédie chez les Hominidés [Origin(s) of Bipedalism in Hominids.
Hürzeler J 1949. Neubeschreibung von Oreopithecus bambolii Gervais.- Schweizerische Palaeontologische Abhandlungen 66(5):1–20.
Köhler M and Moya-Sola S 2003. La evolución de Oreopithecus bambolii Gervais, 1872 (Primates, Anthropoidea) y la condición de insularidad. Coloquios de Paleontología, Vol. Ext. 1 (2003) 443-458.
Nelson SV 2016. Isotopic reconstructions of habitat change surrounding the extinction of Oreopithecus, the last European ape. American Journal of Physical Anthropology 160:254–271. https://doi.org/10.1002/ajpa.22970
Rook L, Bondioli L, Köhler M, Moya-Sola S and Macchiarelli R 1999. Oreopithecus was a bipedal ape after all: Evidence from the iliac cancellous architecture. Proceeding of the National Academy of Science USA 96:8795–8799.
Russo GA and Shapiro LJ 2013. Reevaluation of the lumbosacral region of Oreopithecus bambolii. Journal of Human Evolution, published online July 23, 2013; doi: 10.1016/j.jhevol.2013.05.004

wiki/Oreopithecus

Milwaukee Journal account of the Huerzeler Oreopithecus
Smithsonian Magazine account of Oreopithecus controversies
BBC account of Oreopithecus
SciNews account of Oreopithecus