A REMARKABLE CRANIUM OF PLESIOPITHECUS-TERAS (PRIMATES, PROSIMII) FROM THE EOCENE OF EGYPT

Between 1991 and 1993 specimens of a highly distinctive primate, named Plesiopithecus teras [Simons, E. L. (1992) Proc. Natl. Acad. Sci. USA 89, 10743-10747], were found at site L-41 in late Eocene deposits of the Fayum Depression, Egypt. The most important of these specimens con sists of a nearly complete skull, which facilitates the evaluation of affinities of this primate. Characteristics of the known material now demonstrate that Plesiopithecus is a prosimian, although mandibular mo lar morphology, in particular, bears similarity to that in molars of a rchaic members of Anthropoidea. Plesiopithecus has a postorbital bar b ut lacks posterbital closure, it has upper molars without hypocones, a nd it may retain four lower premolars. Its familial rank was considere d incertae sedis by Simons [Simons, E. L. (1992) Proc. Natl. Acad. Sci . USA 89, 10743-10747]; it can now be demonstrated that Plesiopithecus justifies establishment of a new family and superfamily. The new supe rfamily apparently lies closer to the toothcomb prosimians (strepsirhi nes) than to any other known primate group. Under this interpretation the enlarged, procumbent tooth in the jaw of Plesiopithecus is homolog ous to either the lateral incisor or the canine of the prosimian tooth comb.