Henry Gee

So our nearest relatives, the tunicates, have gone on to be an amazingly diverse and weird set of creatures.

And they go back to the Cambrian explosion as well.

I'd never heard of them before.

Yes, they do.

And they also acquire armour.

Yes.

Now, in the succeeding Ordovician period, from the Ordovician through to the Devonian,

They're more and more armoured fish.

Mostly these are jawless fish.

They just had mouths.

They didn't have, you know, up and down crunching jaws.

Some of them, they had very boxy armoured skeletons.

So the front end was pretty much solidly boxed and the back end had a swishy tail.

Sometimes they had fins on each side and sometimes they didn't.

Yes, but also a later arthropod, which were even more nightmarish.

These were called the Eurypterids, which were relatives of spiders and scorpions.

So these are the original scorpions.

Yeah, and these could be, you know, six to eight feet long, enormous googly eyes, and they really did have snapping pincers.

And Al Romer, the same guy who came up with the idea of the dual origin of vertebrates, he published a paper in Science in 1933 that's a classic, which is he said that maybe vertebrates evolved armor to escape the snapping jaws of Eurypterids.

Now it's kind of fanciful.