Perhaps the greatest tragedy of the saola's placement on this list is that it was only discovered in 1992 and has been sighted so rarely (only four times in the wild), that it has earned the nickname of "The Asian Unicorn." It was the first large mammal discovery in more than 50 years, yet little is known about the saola and none are currently in captivity. saola are found only in the Annamite Mountains of Vietnam and Laos.
One of the most monumental zoological discoveries of our lifetime may have come too little too late, as the rarity of the saola has become it's defining feature -- making study through observation nearly impossible.
Their population is unknown, but is estimated to be a maximum of a few hundred and a minimum of a few dozen. The saola face the very real threat of extinction due to deforestation, accidental catches in hunting snares intended for wild boar, and poaching.
A November 2013 Saola sighting was caught on camera for the first time since 1998. The rare encounter represents a moment of cautious optimism for the World Wildlife Fund, which has helped Vietnamese forest guard patrols remove 30,000 snares and dismantle 600 illegal hunting camps since 2011. You can donate to the organization's international conservation efforts here.