Three-dimensional molar enamel distribution and thickness in Australopithecus and Paranthropus.
Thick molar enamel is among the few diagnostic characters of hominins which are measurable in fossil specimens. Despite a long history of study and characterization of Paranthropus molars as relatively 'hyper-thick', only a few tooth fragments and controlled planes of section (designed to be proxies of whole-crown thickness) have been measured. Here, we measure molar enamel thickness in Australopithecus africanus and Paranthropus robustus using accurate microtomographic methods, recording the whole-crown distribution of enamel. Both taxa have relatively thick enamel, but are thinner than previously characterized based on two-dimensional measurements. Three-dimensional measurements show that P. robustus enamel is not hyper-thick, and A. africanus enamel is relatively thinner than that of recent humans. Interspecific differences in the whole-crown distribution of enamel thickness influence cross-sectional measurements such that enamel thickness is exaggerated in two-dimensional sections of A. africanus and P. robustus molars. As such, two-dimensional enamel thickness measurements in australopiths are not reliable proxies for the three-dimensional data they are meant to represent. The three-dimensional distribution of enamel thickness shows different patterns among species, and is more useful for the interpretation of functional adaptations than single summary measures of enamel thickness.
Olejniczak
A J
AJ
Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany. olejniczak@eva.mpg.de
Smith
T M
TM
Skinner
M M
MM
Grine
F E
FE
Feeney
R N M
RN
Thackeray
J F
JF
Hublin
J-J
JJ
D000818:Animals; D005075:Biological Evolution; D003743:Dental Enamel / Q000033:anatomy & histology*; D015186:Hominidae / Q000033:anatomy & histology*; D021621:Imaging, Three-Dimensional; D008963:Molar / Q000033:anatomy & histology*; D014057:Tomography, X-Ray Computed