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The Leonaspis trilobite has spines for days, and that’s one of the many reasons we love carrying them. The way this specimen has been preserved makes it look like it is slowly sifting through silt on the ocean floor, and that’s probably not far off from what it actually did during its life. It’s a snapshot from the Late Devonian to Carboniferous periods (roughly 360–300 million years ago), when these spiky buddies thrived. Speaking of the spines, scientists think they were used as a defensive mechanism when threatened. After all, who would want to try and make a meal out of a spiked ball?

About trilobites in general:

These ancient marine arthropods are especially famous for their large, highly detailed compound eyes, some of the most impressive ever found in trilobites. Fun fact: trilobites are the only known animals to have eyes made with calcite lenses. Yes, like the crystal calcite. How cool is that?

Their compound eyes were built from tiny lenses made of calcite, a transparent form of calcium carbonate. Each lens sat on top of a photoreceptor cell beneath the exoskeleton. Because trilobite shells were already made largely of calcite, their eye lenses were essentially part of the mineralized exoskeleton.

These creatures thrived on Earth roughly 419 to 359 million years ago, long before the dinosaurs. There’s a gap of about 20 million years between the extinction of trilobites and the appearance of the first dinosaurs. Trilobites were everywhere until the Permian-Triassic extinction event, ominously known as “The Great Dying.” No one knows exactly what happened, but scientists believe a combination of massive volcanic eruptions, extreme climate change, ocean acidification, and low oxygen levels devastated marine ecosystems during this mass extinction.

Considering the scale of that event, you probably won’t be shocked to hear that trilobites have no direct living descendants today. Their closest living relatives are thought to be arthropods, the group that includes horseshoe crabs, spiders, and crustaceans. Sadly, we probably won’t ever see a resurgence of calcite-eyed sea bugs, but nature has a way of surprising even the most astute among us. Guess we’ll have to wait a few million years to find out.