Molar enamel thickness and dentine horn height in Gigantopithecus blacki

Abstract

Absolutely thick molar enamel is consistent with large body size estimates and dietary inferences about Gigantopithecus blacki, which focus on tough or fibrous vegetation. In this study, 10 G. blacki molars demonstrating various stages of attrition were imaged using high-resolution microtomography. Three-dimensional average enamel thickness and relative enamel thickness measurements were recorded on the least worn molars within the sample (n = 2). Seven molars were also virtually sectioned through the mesial cusps and two-dimensional enamel thickness and dentine horn height measurements were recorded. Gigantopithecus has the thickest enamel of any fossil or extant primate in terms of absolute thickness. Relative (size-scaled) measures of enamel thickness, however, support a thick characterization (i.e., not "hyper-thick"); G. blacki relative enamel thickness overlaps slightly with Pongo and completely with Homo. Gigantopithecus blacki dentine horns are relatively short, similar to (but shorter than) those of Pongo, which in turn are shorter than those of humans and African apes. Gigantopithecus blacki molar enamel (and to a lesser extent, that of Pongo pygmaeus) is distributed relatively evenly across the occlusal surface compared with the more complex distribution of enamel thickness in Homo sapiens. The combination of evenly distributed occlusal enamel and relatively short dentine horns in G. blacki results in a flat and low-cusped occlusal surface suitable to grinding tough or fibrous food objects. This suite of molar morphologies is also found to varying degrees in Pongo and Sivapithecus, but not in African apes and humans, and may be diagnostic of subfamily Ponginae.

Three-dimensional molar enamel distribution and thickness in Australopithecus and Paranthropus

“…(2008) interpretation of molar adaptation to diet. Among taxa studied in three dimensions, thick enamel over cusp tips is unique to these australopiths and Gigantopithecus (Olejniczak et al 2008a); these taxa also exhibit relatively short dentine horns (ESM). Thick cuspal enamel coupled with short dentine horns results in a tabular occlusal surface; this molar configuration probably increases molar longevity in response to abrasive diets in small-object feeders, and prevents the formation of cracks at the enamel-dentine junction in large-object feeders (Lucas et al 2008).…”

“…These cross sections were designed to yield proxy measures of the entire tooth crown, since medical imaging techniques were insufficient to record the whole-crown measurements at the time of their development (Martin 1985). These twodimensional methods prohibit the examination of enamel thickness distribution over the entire molar crown (sensu Kono 2004;Olejniczak et al 2008a).…”

New visions of dental tissue research: Tooth development, chemistry, and structure

“…46,[80][81][82][83] Reiko Kono's landmark study 84 firmly established the utility of micro-CT for assessment of three-dimensional (3D) molar enamel thickness and enamel distribution. Three-dimensional enamel thickness data are now available for a broad sample of extant primates, 46,78,84 the fossil ape Gigantopithecus blacki, 85 Neanderthals, 43,86 australopiths, 103 and Middle Stone Age Homo sapiens. 87 New 3D data have confirmed broad trends in primate enamel thickness derived from earlier twodimensional studies 78 and have also demonstrated that thick molar enamel is not found in all fossil hominin taxa.…”

Two-dimensional patterns of human enamel thickness on deciduous (dm1, dm2) and permanent first (M1) mandibular molars

“…1 Measures of the final thickness of that coating have provided important insights into primate taxonomic status [2][3][4][5][6][7] and dietary adaptations. [8][9][10][11][12][13] Others have related variations in enamel thickness upon a single tooth and along the molar row to functional and morphological interpretative models.…”