The purpose of this application, under Articles 23.9.3 and 81.1 of the Code, is to conserve the usage of the species-group name Simopithecus oswaldi Andrews, 1916 by giving it precedence over its senior subjective synonym Cynocephalus atlanticus Thomas, 1884. Theropithecus is a common to dominant member of the extinct primate community across Africa after 4 million years ago (Jablonski & Frost, 2010) and often co-occurred with extinct humans (Hominini); fossils are also known rarely across Eurasia (Roberts et al., 2014). Most fossil samples are currently included in Theropithecus oswaldi (Andrews, 1916), which is often divided into chrono-geographic subspecies. Cynocephalus atlanticus Thomas, 1884 was not recognized as a member of Theropithecus until 1973, and this nomen has seldom been used, but if it were shown (as seems likely) to be conspecific with Simopithecus oswaldi Andrews, 1916, widespread paleontological usage would be upset. It is thus proposed to give conditional precedence to the later name, which would still permit the use of Theropithecus atlanticus as a distinct species or subspecies of Theropithecus oswaldi. Lectotypes are designated for Simopithecus oswaldi olduvaiensis Leakey & Whitworth, 1958 and Simopithecus oswaldi hopefieldensis Singer, 1962.