What’s it about?
Smith presents an argument that all teeth in vertebrates share a common origin, even though they look remarkably different, using evidence from growth lines in fossils, as well as developmental studies of modern fishes to support this.
Why does it matter?
Paleontologists argue that the ‘teeth’ in placoderms (among the most primitive of the jawed fishes) are either homologous to teeth of all modern fishes and terrestrial vertebrates, or that they have a completely different origin. This difference in origin has a profound effect on our interpretations of the origins and evolution of jawed vertebrates.
If Smith’s conclusions are correct, then teeth are among one of the first features that developed in early jawed vertebrates.
Why did I read this?
While I was reading about the origins of jaws in vertebrates, I came across this paper. Since I study teeth almost exclusively, I thought this would be an interesting paper to read.
What did I learn?
I’ve always thought that teeth were ectodermal in origin. This could be what I was taught way back when, or it could be faulty memory. This paper show that it is the interaction of ectoderm and endoderm that result in the development and pattern of teeth in jaws.