Probably, the tooth and the nature of their shift (where there’s new teeth and how they displaced the old jaw) bony fish closer to the original than previously thought, reported in Science. This assumption paleontologists made on the basis of analysis of the maxillary bone, basal placoderm acanthoceratid. It turned out that they, like some bony fish teeth were located on the edges of the jaws, fastened to the integument, and to the jaw bones, and a new one grew from the language (internal), not the “cheeks” (outside). Previously, the closest to the original state thought teeth of other extinct clustertech — artrodar.
The first vertebrates do not have teeth, and they, like modern lampreys, cost Horny growths on “language”. It is now believed that the teeth appeared more than 400 million years ago from tubercles covering the plates on the jaws of the primitive fish. It is probably the teeth had no roots and as it peels off to the outside, but inside they were replaced with more young. However, the bony fish and terrestrial vertebrates the teeth are in the jaw grooves, and so they fell, to dissolve their Foundation. Similar happens in humans when the milk teeth are replaced by permanent.
Different fish (as have many others, but the fish in this context, important as they are closer to the first toothed pozvonocna) teeth grow from different sides of the jaw bone: the crown group (the most distant from a common ancestor) bony fish they are shifted longitudinally and artrodar (extinct group of primitive clustertech) new teeth could grow and the language, and external (“cheek”, although the cheeks they have) side and longitudinal rows. Which of these initial States, not completely understood.