An examination of dental development in Graecopithecus freybergi (=Ouranopithecus macedoniensis)

This study examined enamel thickness and dental development in Graecopithecus freybergi (=Ouranopithecus macedoniensis), a late Miocene hominoid from Greece. Comparative emphasis was placed on Proconsul, Afropithecus, Dryopithecus, Lufengpithecus, and Gigantopithecus, fossil apes that vary in enamel thickness and patterns of development. In addition, comparisons were made with Paranthropus to investigate reported similarities in enamel thickness. Several sections of a right lower third molar were generated, from which enamel thickness and aspects of the enamel and dentine microstructure were determined. Data from parallel sections shed light on the effects of section obliquity, which may influence determination of both enamel thickness and crown formation time. Graecopithecus has relatively thick enamel, greater than any fossil ape but less than Paranthropus, with which it does show similarity in prism path and Hunter-Schreger band morphology. Aspects of enamel microstructure, including the periodicity and daily secretion rate, are similar to most extant and fossil apes, especially Afropithecus. Total crown formation time was estimated to be 3.5 years, which is greater than published values for modern Homo, similar to Pan, and less than Gigantopithecus. Data on dentine secretion and extension rates suggest that coronal dentine formation was relatively slow, but comparative data are very limited. Graecopithecus shares a crown formation pattern with several thick-enamelled hominoids, in which cuspal enamel makes up a very large portion of crown area, is formed by a large cell cohort, and is formed in less than half of the total time of formation. In Paranthropus, this pattern appears to be even more extreme, which may result in thicker enamel formed in an even shorter time. Developmental similarities between Paranthropus and Graecopithecus are interpreted to be parallelisms due to similarities in the mechanical demands of their diets.