Fossils collected more than 150 years ago show that the techniques some creatures use for defensive curling have not changed in millions of years.
When the going got tough in the Paleozoic Era, trilobites rolled up. Armed with sturdy exoskeletons, these ancient arthropods curled up like armadillos to avoid predators or dangerous environmental conditions on the seafloor.
Many trilobites have been found with their exoskeletons fossilized in a curled position, as if holding a perpetual stomach crunch. But few of these fossils preserve the internal anatomy that trilobites used to form a defensive ball.
“While enrolled trilobite fossils are really common, we don’t have any of the ventral soft tissue preserved,” said Sarah Losso, a Ph.D. candidate at Harvard University who specializes in trilobite evolution.
Ms. Losso and her colleagues may have finally unfurled the mystery of tumbling trilobites by using a cache of impeccably preserved fossils. Their findings, published on Wednesday in the journal Proceedings of the Royal Society B, describe the interlocking anatomy of a rolled-up trilobite for the first time.
The trilobite fossils examined in the new study came from central New York’s Walcott-Rust Quarry, where a mudslide 450 million years ago smothered an entire community of the scuttling sea creatures. Discovered by the paleontologist Charles Doolittle Walcott in 1870, the site yielded the first traces of trilobite appendages and soft-tissue features like gills.
Walcott’s trilobite fossils, and thin sections he sliced out of them, are stored at the Museum of Comparative Zoology at Harvard University. Ms. Losso was analyzing the trilobites’ appendages when she came across a curled Ceraurus trilobite with a set of plates called sternites lining its stomach that rarely survives fossilization. “When I found that specimen, that’s when I got excited,” Ms. Losso said. “We don’t have these plates in enrolled, three-dimensional specimens.”
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