Evolution and development of teeth

Teeth as a feeding mechanism in an oral cavity (mouth) are functionally and locationally linked with jaws. In fossils, teeth found in the oral cavity are usually linked with jaws, although mineralised structures with the same histology as teeth are known in fossils before jaws appeared. Denticles in the skin occur in both fossil and extant fish. Pharyngeal denticles also o ccur in both extant and fossil gnathostomes but in only a few fossil agnath ans (thelodonts). Complex structures with dentine and enamel have been desc ribed in the earliest jawless vertebrates, conodonts. Such fossils have bee n used to suggest that teeth and jaws have evolved and developed independen tly. Our understanding of the developmental biology of mammalian tooth deve lopment has increased greatly in the last few years to a point where we now understand some of the basic genetic interactions controlling tooth initia tion, morphogenesis and patterning. The aim of this review is to see what t his developmental information can reveal about evolution of the dentition.