User:Abyssal/Portal:Silurian/DYK/3

...that ostracoderms are the earliest known vertebrate animals?
... that fossils of the extinct bivalve family Praenuculidae have been found on every continent except Antarctica?
... that Arthropleuridea is an extinct class of myriapods which includes, at over 2 meters long, the largest terrestrial arthropods that ever lived?