Prisms and tubules in multituberculate enamel.

Abstract

Upper Cretaceous multituberculate tooth enamel was investigated by light microscopy, scanning electron microscopy and contact microradiography. The spatial arrangement of the crystallites in the enamel was well defined in prisms and interprismatic enamel. The diameter of the prisms and their mutual central distances were far greater than in the enamel of any known representative of present mammals. It is concluded that true prismatic enamel also existed in non-therian primitive mammals. Enamel tubules were present and were direct extensions of dentinal tubules. The enamel tubules crossed the course of the prisms and in cross-sections were found to be present in the interprismatic enamel as well as in prism cores. It is difficult to conceive that such tubules could be the product of ameloblasts, and it is concluded that they have a dentinal origin.