Phylogenetic memory of developing mammalian dentition

Area of Science:

• Developmental Biology
• Evolutionary Biology
• Paleontology

Background:

• Atavisms and vestiges represent the reappearance of ancestral traits in modern organisms.
• Vestigial teeth are regularly found in species, while atavisms are exceptional occurrences.
• Understanding these dental structures provides a window into evolutionary pathways.

Purpose of the Study:

• To survey and update data on vestigial and atavistic teeth in mammals.
• To discuss the ontogenetic and evolutionary implications of these dental structures.
• To explore potential homologies between mammalian teeth and ancestral vertebrate dentition.

Main Methods:

• Survey of existing literature on mammalian vestigial and atavistic teeth.
• Analysis of recent findings from mouse and human embryonic development.
• Comparative developmental and morphological analysis.

Main Results:

• Transient dental placodes in mouse embryos resemble early reptilian tooth primordia.
• Vestigial buds in mice suggest the evolutionary loss of premolars, with one potentially incorporated into the first molar.
• Developmental patterns in human embryos show similarities to 'Zahnreihen' in lower vertebrates.

Conclusions:

• Atavistic supernumerary teeth can arise from aberrant development of ancestral tooth primordia.
• Homologies may exist between mouse molars and human deciduous premolars/first molars.
• A developmental link is hypothesized between mammalian external dentition structures and reptilian/lower vertebrate teeth.