CIRCUMNATAL STATUS OF MOLAR CROWN MATURATION AMONG HOMINOIDEA

The permanent first molars of the Pongidae, Hylobatidae and Hominidae are compared at the circumnatal and the eruptive stages. The calcification of the cusps of these molars at the time of birth is similar in all of the species with the exception of the gibbon which is advanced. The M1 of the pongids and man have three cusps calcified at the time of birth. They are the protoconid, metaconid, and the hypoconid, and the sequence of calcification follows this order. The entoconid on the orangutan M1 bud is calcified on the tip. The entoconid of the gibbon M1 is also calcified, but to a greater extent, and the mesial cusps have a calcified bridge between them. The M1 has three cusps calcified at the time of birth. The paracone, protocone and metacone are calcified in this sequence. The gibbon has all four cusps with varying degrees of calcification. Detailed scrutiny of the erupted M1 and M1 reveals marked differences in the morphology and size of these molars amongst the anthropoid apes and man. Although there are differences in these molars at the time of birth, they are not as dissimilar as are the erupted forms. The traits that distinguish the molars of the various species are present on the newborn bud but are attenuated. Mensurational data are presented in a graphic form to illustrate trends in growth. © 1969.