Enamel micromorphology of the tribosphenic molar

The tribosphenic molar is an ancestral type of mammalian teeth and a phy- lotypic stage of the mammalian dental evolution. Yet, in contrast to derived teeth types, its enamel microarchitecture attracted only little attention and the information on that subject is often restricted to statements suggesting a simple homogenous arrangement of a primitive radial prismatic enamel. The present paper tests this prediction with aid of comparative study of eight model species representing the orders Chiroptera, Afrosoricida, Eulipotyphla (Erinaceomorpha) and Eulipotyphla (Soricomorpha). Spe- cial attention was paid to shrews (Soricidae), the group with most derived tribosphenic dentition among extant insectivores. The detailed electron microscopic (SEM) analysis of standardized cross sections over essential structural elements of tribosphenic molars (in shrews supplemented with sections of the lower incisor, the most derived tooth of the dentition) was a basic source of information. The results demonstrated common arrangements related to tribosphenic design (he- terotopy of enamel thickness, radial prismatic enamels as primary product of ameloge- netic activity), yet, an unexpectedly broad span of variation in state of further variables was discovered at the same time. The taxon-specific arrangements and..