Scanning electron microscopy of molar enamel structure of cricetodontine neogene rodents.

Ultrastructural characters of enamel were studied as a phylogenetic indicator in a family of rodent fossils: the Cricetidae. The extinct group Cricetodon-Ruscinomys is a known lineage which span 17 million of years (from -20 My to -3 My). The three-dimensional organization of enamel of the left M1 was studied in 8 cricetid species at three different levels: (1) the chewing surface; (2) the middle of the crown; (3) the cervical part, close to the root. The arrangement and other details of enamel prisms varied according to five factors: (1) tooth morphology (there were differences between the four faces of the same molar); (2) enamel thickness; (3) level of crown; (4) degree of hypsodonty; (5) chronological age of the extinct species.