Which of these is one of the earliest-known groups of arthropods?

They remind me of horseshoe crabs

Sobering to think they were around many millions of years longer than we have and they no longer exist. How long will we exist?

Player #25874027, I actually have a fossil of one

I recognised that they are fossils so are likely to have been the earliest group

thank you Dinosaur Train

Player #3503313, they remind me of woodlice