Plesiopithecus teras, the only species so far identified, was discovered in 1992 by Elwyn L. Simons in Egypt at the base of the Jebel Qatrani Formation at Fayum in quarry L-41.

Plesiopithecus was a medium-sized strepsirrhine primate, with large orbits, a high muzzle, and a skull exhibiting klinorhynchy (a marked angle between the palate and the basicranium, or the lower region of the braincase).

[2] The cranial and dental morphology of Plesiopithecus resemble what is predicted of an aye-aye ancestor, with an arched cranial vault suggesting klinorhynchy (a marked angle between the palate and the basicranium, or the lower region of the braincase) similar to that of aye-ayes, significantly enlarged canines and/or incisors, reduced molars and premolars,[12] a high muzzle, and anteriorly placed orbits.

[12] Key to this possible close affinity with the aye-aye is the identity (canine vs. incisor) of the procumbent front teeth of both species, neither of which is definitively known.

The holotype, which was found at the base of the Jebel Qatrani Formation at the Egyptian Fayum in quarry L-41 and dated to the latest Eocene,[13] included a right mandible with intact dentition ranging from the third molar up to the first anterior tooth.

[1] Simons acknowledged that the taxonomic interpretation was complicated,[14] though he initially decided to classify under superfamily Hominoidea (apes)[1] due to its flat and broad lower molars.

Its bizarre and specialized traits made it difficult to classify until the discovery of its skull, reported in 1994, showed it had a postorbital bar, proving that it was a strepsirrhine primate.

[13] Prior to Simons' discovery of the right jaw, one of its molars had been found a few years earlier and incorrectly attributed to an Eocene lorisoid.

Due to cranial and dental similarities with the aye-aye and signs of wear on the tips of its front teeth, it is thought to have bored holes in wood in search of soft-bodied insects, which likely make up its diet.