Outside Freehold, N.J.–The water is icy cold and the stone is slippery as I wade in up to my calves. Along the banks of this slow-flowing stream, guarded by prickly brambles, lies one of the richest caches of fossils dating back to the extinction that claimed the dinosaurs. The remains of marine creatures buried here, kept secret to prevent looting, tell an unusual tale: rather than dying off 65 million years ago, these creatures lived on afterward, albeit briefly. The discovery is causing scientists to rethink why some creatures survived the so-called KT extinction while others did not.

Unlike this one, significant fossil sites tend to be found in exotic locales such as the searing hot Gobi Desert or the windswept pampas of Patagonia, areas remote from the kind of urban development that can ruin them. “You don’t expect to find them here in suburban New Jersey some 90 minutes away from New York City,” explains Neil Landman, curator of fossil invertebrates at the American Museum of Natural History.

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