Historic numbers of animals across the globe have become endangered or pushed to extinction. But some of these species sit in limbo — not definitively extinct yet missing from the scientific record. Rediscovering a "lost" species is not easy. It can require trips to remote areas and canvassing a large area in search of only a handful of animals. But new technology and stronger partnerships with local communities have helped these hidden, "uncharismatic" creatures come to light.

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The species, including birds, mussels and a bat, have been moved off the threatened and endangered list. They join 650 other species that have gone extinct in the U.S.

On Wednesday, John Hume, owner of the Platinum Rhino Project, launched an auction to sell off the 2,000-strong herd in an online sale that's starting at $10 million.