In an image provided by the Bureau of Land Management, cave specialist Bryan McKenzie rappels into Natural Trap Cave in north-central Wyoming during a cleanup expedition. The cave holds the remains of tens of thousands of animals, including many now-extinct species, from the late Pleistocene period tens of thousands of years ago. Starting July 28, 2014, scientists plan to venture back into the cave and resume digging for the first time in more than 30 years. (AP Photo/Bureau of Land Management)
CHEYENNE, Wyo. – For the first time in more than 30 years, paleontologists are about to revisit one of North America's most remarkable troves of late Pleistocene fossils: The bones of tens of thousands of animals piled at least 30 feet deep at the bottom of a sinkhole-type cave.