A new display at the American Museum of Natural History includes some of the oldest fossils on exhibit. Called trilobites, some of these extinct marine arthropods are more than 500 million years old. (Just as one comparison, Tyrannosaurus rex lived from about 85 to 65 million years ago.)

Photo: © AMNH/R. Mickens

Trilobites first evolved about 520 million years ago, during the Cambrian Period, when the planet was mostly covered by water. “The world looked very different then,” notes Neil Landman, curator in the Division of Paleontology, “and there were stretches of ocean that no longer exist.”

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Cambrian trilobites shared the shallow seas with jellyfish and primitive mollusks such as snails and clams, along with annelid worms and sponges. “There were no vertebrates, of course,” says Landman, “nor, at that time, was there life on land.”

Photo: © AMNH/D. Finnin

Trilobites’ shells were made of the mineral calcite, like clam- or crabshells. They were also the earliest known life forms with compound eyes—eyes with multiple lenses. Some trilobites had eyes on stalks, perhaps for peering above the sediment in the waters where they lived.

Check out more photos of the trilobite fossils here.

Can you name the oldest fossil on display at the Museum? You'll find the answer here.

Photo: © AMNH/R. Mickens