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Credit: Photo by Lance Grande from The Lost World of Fossil Lake: Snapshots from Deep Time, © 2013, published by the University of Chicago Press.
The creatures in this gallery were all entombed at the bottom of Wyoming's long-gone Fossil Lake, which was teeming with life during the early Eocene, about 52 million years ago. Only one frog has ever been found at the formation. The single specimen pictured here measures just 1.6 inches (4 cm) long. It has yet to be given a taxonomic classification by scientists.