Compared to other great apes, the canines are short, the enamel is thin, and the molars are flatter.

The species name is in honour of the late Japanese geologist Katsuhiro Nakayama who worked on the expedition.

Ouranopithecus, in turn, is postulated to be closely related to australopithecines and the human line.

[3] A 2017 study on deciduous fourth premolars—deciduous teeth are less affected by environmental factors as they soon fall out and are replaced by permanent teeth—found that Nakalipithecus and later African apes (including australopithecines) shared more similarities with each other than to Eurasian apes, though drew no clear conclusion on the Nakalipithecus–Ouranopithecus relationship.

The mandible is less robust (heavily built) than those of contemporary Eurasian Miocene apes, except for Ouranopithecus.

[3] Climate change caused the expansion of grasslands in Africa from 10–7 million years ago, likely fragmenting populations of forest-dwelling primates, leading to extinction.

[6] Nakali has also yielded a black rhino specimen,[7] the pig Nyanzachoerus, an antelope, the hippo Kenyapotamus, the rhino Kenyatherium, the giraffe Palaeotragus,[8] the horse Hipparion,[9] the elephant-like proboscideans Deinotherium and (possibly) Choerolophodon,[8] and the colobine monkey Microcolobus.