PREMOLAR DEVELOPMENT AND ERUPTION IN THE EARLY EOCENE ADAPOIDS CANTIUS RALSTON I AND CANTIUS ABDITUS (MAMMALIA, PRIMATES)

摘要

— New specimens of early Eocene Cantius ralstoni and Cantius abditus are described that show the sequence of lower premolar development and eruption to have been P2-P4-P3 in early adapoids. This is the sequence documented for living Tupaioidea, some extant Lemuroidea, and living Tarsius representing Tarsioidea. It is also the developmental sequence documented for Eocene Notharctus and Darwinius, and for Miocene Sivaladapis within Adapoidea. Broad distribution of a 2-4-3 sequence of premolar development in tree shrews and primitive groups of living primates, and presence of this sequence in early Eocene primates indicates that this is the primitive sequence of development for Primates as an order. Adapis and Leptadapis have a premolar eruption sequence, 4-(2-3), that differs from the sequence in Cantius, Notharctus, and other Adapoidea. Eruption of P2 before both P3 and P4 in early Eocene Cantius supports interpretation of the small anterionnost upper and lower premolars in Darwinius masillae as permanent P~2 and P_2 rather than deciduous teeth.