Dr. Yara Haridi

Oh, no.

Their mouth is always open because they don't have jaws yet.

So these little tooth like things that are on the outside of these fish, we call them odontodes.

So that's a word I'm going to be using.

So odontodes are little chunks that basically look like a tooth, but they're on the outside of the mouth.

They're made of enamel and dentine and they have a pulp cavity, but they cover the outside of fish rather than being inside of the mouth.

Boom, exactly.

We don't know.

Or we didn't know.

We had a couple of hypotheses.

Why would you have these things on the outside of your body?

The very first answer was always like protection.

Like, oh, you're making your hardest tissue on the outside of the body to make armor.

You know, a lot of modern fish do that.

Things like gar have really hardened scales that cover their entire bodies.

Makes it harder for things to bite you.

Makes it harder for parasites to get attached, etc., etc.,

And of course, the image of like teeth outside the mouth is so grotesque.

But if you think about like modern sharks, modern sharks have teeth outside the mouth or they have these odontos.

They're covered in them.