Evolutionary implications of tooth replacement in the Paleocene mammal Pararyctes

Abstract

A specimen of the palaeoryctid Pararyctes (Mammalia: Eutheria), from Paleocene strata of Alberta, shows nearly the complete replacement pattern of the dentition. Unexpectedly, premolars at two positions are seen replacing dP4, whereas the premolars at the anteriormost three positions seem not replaced or shed. The resulting total of concurrently functional teeth at five premolar and three molar positions, while mimicking that in certain ancestral eutherians, is clearly a derived character state, achieved independently. Furthermore, this pattern is inconsistent with the assumptions that deciduous and permanent teeth need belong to the same tooth families and that identical adult dental formulae are secure guides to homology.