Tooth onoteny in Didelphis virginiana (Marsupialia : Didelphidae)

The ontogenetic development of the teeth was studied in a series of seven specimens of Didelphis virginiana whose crown-rump length varied from 11 to 49 mm. Though all developing teeth showed undifferentiated lingual downgrowths of dental lamina, there was no evidence of any non-functional teeth. No more than five upper incisors were present at any one time. The metacone was the first cusp to calcify in the upper deciduous and fist permanent molar teeth. The protoconid was the first cusp to calcify in the lower molar teeth. The results were compared with findings from a recent study of tooth ontogeny in Antechinus flavipes.