These larger specimens feature at least one, but in most cases, multiple Elrathia kingii trilobites embedded in stone.

Of the more than 20,000 species of trilobites, Elrathia kingii are some of the best preserved ones you can find. And that’s not just luck! These guys fossilized so well because of where they lived – low-oxygen waters. Low oxygen meant there weren’t any decomposers around to break them down, letting them turn into perfect little fossils once they got buried by underwater sediment.

These trilobites are preserved in incredible detail, and now, that detail comes supersized, with each of these "SciShow Boulders" offering a unique arrangement of preserved fossils.

Each piece measures roughly 2–5 inches across, and no two are alike. We have a very limited number of these larger specimens, so once they’re gone, they’re gone.

Perfect as a paperweight, a conversation starter, or just an awe-inspiring chunk of Earth’s history.