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.
Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany. olejniczak@eva.mpg.de
A J
AJ
Olejniczak
T M
TM
Smith
M M
MM
Skinner
F E
FE
Grine
R N M
RN
Feeney
J F
JF
Thackeray
J-J
JJ
Hublin
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