On a hot August day in 2005 my team and I were out hunting for fish fossils in the tall, grassy paddocks of Gogo Station, a vast cattle ranch located in the heart of northwestern Australia. Today the arid region is hardly suitable for aquatic creatures. But some 375 million years ago, during the Late Devonian period, a shallow sea covered the area and Gogo was home to an enormous tropical reef that teemed with marine life, including a plethora of primitive fishes. Luckily, many of their remains have survived across the ages. Nestled among the clumps of spiky Spinifex bushes and sleepy death adders lie softball-size nodules of limestone—the products of millions of years of erosion of the local shales—some of which harbor pristine fossils of the fishes that lived on the primeval reef. And so over the course of our terrestrial fishing expedition, we would spend our days cracking the nodules open, one after another, hoping to glimpse a treasure inside.