Tooth ultrastructure of late triassic Haramiyidae.

Six molars of Haramiyidae from the French lower Rhaetic were examined by scanning and transmission electron microscopy, and by electron diffraction. Typical polished wear facets were located on the tops and on the occlusal bases of cuspids. Enamel was found to have had a structural pattern defined as "pre-prismatic", consisting of a repetitive pinnate orientation of the c-axes of apatite crystallites but without interprismatic material. Peritubular dentin was not found, but hydroxyapatite deposition in the dentinal tubular lumens was observed, whereas typical denticles with dentinal tubules and hydroxyapatite deposits were located in the pulp chambers. Taken together, these different features are strongly indicative of mastication, and hence enforce the suspected mammalian status of the Haramiyidae.