Ancient Arctic fish rewrites the teeth-and-jaws origin story

A 400-million-year-old jawed fish fossil from the Arctic, Romundina gagnieri, shows that teeth grew on tooth plates in the roof of its mouth, with newer teeth added from the center outward rather than from the back. This finding suggests teeth and jaws appeared earlier and with more flexible patterns than previously thought, reshaping our view of vertebrate tooth evolution and its connection to placoderm ancestors, aided by non-destructive synchrotron imaging.