Development of the teeth in a pouch-young specimen of Isoodon obesulus and one of Perameles gunnii (Peramedidae: Marsupialia)

Vestigial structures and variation in the evolution of the marsupial mammal dental development—a study of the woolly opossum Caluromys philander

The pattern of dental replacement in marsupial mammals has received much attention for its derived nature and potential relationship to the life history of the group. However, few species have been studied thoroughly, and little is known about the embryonic structures and their use in addressing issues of homology and dental evolution in general. We studied a developmental series of ten individuals of pouch young Caluromys philander to thoroughly document dental development with histological sections and 3D models of dental series. We report that the successor P3 arises from a lingual successional lamina from its predecessor dP3. The germs of vestigial, unerupted deciduous incisors and canines are present alongside their respective permanent successors. These discoveries demonstrate significant differences from the developmental patterns reported for Didelphis and Monodelphis and illustrate that an unsuspected diversity of dental ontogeny is not reflected in the adult pattern of mineralised, erupted or almost erupted teeth.

A discussion of dental homology with reference to primates

The inconsistencies which exist when the traditional tooth-to-bony-landmark/tooth-to-occlusal-relationship criteria of identification of teeth are maintained are discussed. It is pointed out how these (e.g., "the canine is the tooth behind the premaxillary-maxillary suture") can be falsified. It is also suggested that some mammals, including Tarsius and Homo sapiens, develop homologies of three sets of "teeth," and that the "adult" antemolar dentition of a mammal may be composed of retained deciduous teeth as well as permanent teeth. Following a revision of dental homologies in most primates, an approach to reevaluating dental homologies is proposed, and a model of tooth "loss" presented.