Oligopithecidae is notable for which of the following characteristics?

Oligopithecidae is a family of primates that is significant in the study of primate evolution due to its characteristic of postorbital closure. This feature refers to the bony encasement around the eye socket that provides support and protection for the eye, indicating a different ecological adaptation and lifestyle than earlier primate forms. The presence of postorbital closure is associated with a stronger reliance on vision, which is a crucial factor in the social and foraging behaviors of these primates.

The other characteristics mentioned do not apply to Oligopithecidae. A broad pelvis, while important for species adapted to bipedalism, is not a defining trait of this family. Knuckle-walking pertains to certain groups of primates, such as certain great apes, which is not relevant to Oligopithecidae. Lastly, bipedal locomotion refers to the ability to walk on two legs, a trait primarily associated with hominins, but not with Oligopithecidae, whose adaptations do not include this form of locomotion. Thus, postorbital closure stands out as the correct characteristic linked to the Oligopithecidae family.