The nature of the transition in the dental mechanism from pongids to hominids

Abstract

Many recent discoveries of Ramapithecus, and of probably ground-living dryopithecines, Dryopithecus (subgenus Sivapithecus), clarify the nature of the transition of the dental mechanism from that of pongids to the hominid stage with reduced canines and flattened cheek teeth with thick enamel. Faunal correlation with potassium/argon dated sites indicates that Sivapithecus and Ramapithecus appeared in the Old World about the same time, approximately 13 million years ago. The thickened molar enamel of these hominoids suggests a terrestrial adaptation in both groups, probably resulting from climatic changes. This adaptation was not necessarily a unique event in the ancestry of the two genera, for species of the two seem to have been different sizes when the change was made. New Ramapithecus finds come from Pyrgos, near Athens, from Çandir in Anatolia, and from Rudabánya, Hungary. At the latter site various specimens preserve all upper and lower teeth in place, while the Çandir and Pyrgos mandibles give important new information about symphyseal structure and orientation, as well as about arcade arrangement. The Rudabánya finds confirm, as do the others, marked facial foreshortening, relatively orthal incisors, anteriorly abbreviated mandible and canine reduction in Ramapithecus. The dental mechanics of Ramapithecus suggested from earlier described finds recovered in the Siwalik deposits of India and Pakistan, as well as at Fort Ternan, Kenya are clarified by the finds from Athens, Anatolia, and Hungary. Like Australopithecus, Ramapithecus mandibles have well-developed double transverse, shallow but transversely thick horizontal rami and anteriorly shifted, vertically oriented, deep ascending branches. These addes resemblances increase the probability that Ramapithecus is in or near the ancestry of Australopithecus and other hominids.