Preserved by ancient microbial mats, these fossilized trilobite relatives allow scientists to glimpse Silurian life. Photo courtesy of the University of Wisconsin–Madison Geology Museum
Hakai Magazine has a story about a special fossil deposit in Waukesha, Wisconsin. The deposit dates to the Ordovician Period about 440 million years ago. It was discovered in 1984 by amateur paleontologists Jerry Gunderson and Ron Meyer. They found fossilized soft tissue why splitting open rocks from a thin layer called the Brandon Bridge Formation. They realized they had come across something ultra-rare and donated their finds to the University of Wisconsin Geology Museum.
These fossils offer an unparalleled glimpse into the Silurian, a geological period during which Earth’s climate stabilized, plants conquered land, and fish developed jaws. “There’s a lot of really important events that are occurring in the Silurian, and we actually get to see some of these things with the Waukesha” fossils, says Andrew Wendruff, a paleontologist at Ohio’s Otterbein University.
And what a glimpse those Waukesha fossils provide. Although most creatures found in the formation lack easily fossilized hard tissue, they appear on the rock in exquisite detail: Several trilobites sport preserved guts, while some tiny crustaceans no bigger than Altoids possess 440-million-year-old hearts. “To be able to look at this specimen of a leech and actually see the segmented rings and the mouth structure preserved hundreds of millions of years ago is mind-blowing,” says Carrie Eaton, the Geology Museum’s curator.
For decades, this incredible preservation of soft tissue stumped scientists. “Often, there’s this cookie-cutter definition of rapid burial,” Wendruff says. “But what we have here is very different.” In a recent study, Wendruff attempted to answer this question by examining thousands of Waukesha fossils. It turned out that the answer had been there all along, adorning the shale in deep folds like elephant skin.