Development of deciduous and permanent dentition in Tarsius and its phylogenetic significance.

The earliest stages of development and differentiation of deciduous and permanent teeth were studied in prenatal and perinatal tarsiers. Both deciduous and successional teeth develop at loci for I1, I2, C, P2-4. Relationships among the dental lamina, enamel organs, and successional lamina were used to determine tooth homologies. During the second half of prenatal life, dP2 and dI2 undergo abnormal development. Their dentin becomes fragmented, and these teeth are shed or resorbed without eruption during the perinatal period. Our study provides evidence of an intermediate phase in evolutionary tooth loss. These findings do not corroborate recent hypotheses of primate phylogeny based mainly on tooth eruption patterns.