This fossil immortalizes stingray sex of the Eocene. The male and female fat-tailed stingrays (Asterotrygon maloneyi) shown here were likely mating or just about to mate when they were killed, researchers believe.
With just two inhabited buildings and a population of five, Fossil, Wyo., is all but a ghost town today. But as far as ghosts go, the ones at Fossil are pretty remarkable — 50-million-year-old monitor lizards, stingrays and freakishly long-tailed turtles among them.
Fossil showed promise of becoming a train-stop city during America's westward expansion. The town's real golden age, however, may have been the early Eocene, when it was covered in a subtropical lake with an incredible diversity of aquatic life, surrounded by lush mountains and active volcanoes.
Over thousands of years, dead animals rained down into the muck deep below the surface of long-gone Fossil Lake. Their bones mixed with a limey ooze, created by calcium carbonate deposits carried to the lake bottom by rivers flowing in from nearby mountains. These deposits would eventually build up so much — there were sediments piled hundreds of feet thick — that the very bottom layers would be compressed into limestone.
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