Marginal dentition and multiple dermal jawbones as the ancestral condition of jawed vertebrates

Abstract

Teeth and jaws The first vertebrates were jawless, much like a modern hagfish. There has been a lot of interest in how these forms transitioned to having jaws like most of their descendants, including humans. Much of our understanding of this process has focused on how the teeth are replaced relative to the jaw. Previous theories suggested that tooth growth that occurred lingually—or from inside out as in modern fishes—was a derived condition. Vaškaninová et al. vertebrates, suggesting that it may have been ancestral. Science , this issue p. 211