Eastern gorilla
Grauer's gorillas and mountain gorillas were previously thought to be two of the three subspecies of one single species, the gorilla ("Gorilla gorilla"). However, genetic research has shown that the two eastern subspecies are far more closely related than the western subspecies: the western lowland gorilla ("G. gorilla gorilla"), which justified the separate classification. The two eastern subspecies are now classified as "G. beringei".
Biretia
The smallest of the species, "B. fayumensis", had an estimated weight of 273 g, while the largest, "B. megalopsis", had a weight of about 376g. Adaptations of the skull of "B. megalopsis" are easily comparable to the modern tarsiers, a small, modern Asian primate with a nocturnal insectivorous lifestyle. We can infer the possibility of a nocturnal lifestyle for "B. megalopsis"' from the animal's molar roots, which are truncated to accommodate for large eye sockets typical of a nocturnal primate. The large eye structure and similarity to the modern tarsiers also suggests that it has lost its tapetum lucidum. Thus, "B. megalopsis" demonstrates itself as being the oldest known nocturnal primate.