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A high frequency of occurrence of the metaconule was ob­served in maxillary molars of an Australian Aboriginal population. The frequency and degree of expression of the trait increased distally along the molar series from dm2 to M3, whereas fluctuating asymmetry decreased. The morphogenetic field for metaconule expression therefore appeared to be centered around M3 rather than dm2 or Ml as commonly described for other dental characters. Based on a quasi-continuous threshold model, a genetic contribution to metaconule variability was observed, but differences in the timing and duration of odontogenesis between molar tooth germs are most likely to influence penetrance and expressivity. The metaconule may provide additional enamel bulk on the distal occlusal surface of maxillary molars, an area which is subjected to early attrition by opposing teeth during mastication in Aboriginals.