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Proteopithecus Temporal range: [1]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Primates
Family:	†Proteopithecidae
Genus:	†Proteopithecus Simons, 1989
Species:	†P. sylviae
Binomial name
†Proteopithecus sylviae Simons, 1989

Proteopithecus is an extinct genus of early anthropoid primates that lived in Egypt during the late Eocene. The genus has only one species, Proteopithecus sylviae.^[2]

Its fossils are known from Quarry L-41 in the Fayum Depression and include cranial, dental, and postcranial remains.^[3]

The fossils of Proteopithecus were discovered in 1987 and 1988 at Quarry L-41 in the Fayum Depression of Egypt. The genus was formally described by Elwyn L. Simons in 1989, based initially on a left maxillary specimen (CGM 41886). At the time, it was classified alongside Catopithecus and Oligopithecus within the subfamily Oligopithecinae of the family Propliopithecidae.^[2]

Other discoveries provided additional material. In 1997, these discoveries were used to establish the family Proteopithecidae, distinguishing Proteopithecus from other simians found in the Fayum.^[4]

Proteopithecus was a small-bodied primate. Its skull has a relatively broad, rounded braincase, elongated nasal bones, and a lacrimal bone positioned within the orbit. The temporal lines converge towards a small sagittal crest at the rear of the skull. Its cranial anatomy exhibits several derived features characteristic of anthropoids despite its small size.^[4]

Its dentition retains three premolars in each quadrant, with a dental formula of 2.1.3.3. This condition distinguishes it from other simians that possessed only two premolars. The upper molars have distinct hypocones on the first and second molars, while the first upper molar also bears a paraconule. A hypocone-like cusp is present on the fourth upper premolar.^[5][4][6]

Differences in canine size among specimens have been investigated as evidence of sexual dimorphism. A study of Egyptian Eocene anthropoids discussed variation in canine size in Proteopithecus and Catopithecus.^[6]

Proteopithecus sylviae exhibited sexual dimorphism in canine size, a degree of variation not known among living primates of similarly small body size.^[6]

Body mass has been estimated at 250 grams. Its ecology and cranial specimens suggested an arboreal lifestyle, diurnal activity and a diet with fruit and insects.^[6]

Proteopithecus was the first Eocene anthropoid for which associated postcranial remains were described. Its hindlimb anatomy resembles that of platyrrhines and suggests adaptations for substantial amounts of running and pronograde quadrupedal leaping.^[3]

The pronounced canine dimorphism has been thought to be evidence for a polygynous mating system and intense male-male competition.^[6]

The evolutionary relationships of Proteopithecus remain uncertain. Its dental morphology was initially interpreted as resembling that of platyrrhines, the group comprising modern New World monkeys, leading to the suggestion that proteopithecids might be near the base of the radiation that produced them.^[4]

A 2001 review of dental evidence regarded Proteopithecus sylviae as an archaic anthropoid of uncertain familial affinity, illustrating the difficulty of resolving relationships among the earliest anthropoids from fragmentary fossils.^[7]

A 2013 study of the calcaneus attributed to Proteopithecus found similarities with the foot bones of parapithecoids, an extinct group of anthropoids. Its phylogenetic analysis supported a placement of Proteopithecidae as the sister group of Parapithecoidea, although the authors noted that anatomical similarities may reflect shared ancestry or convergent evolution.^[8]