One of the rarest animals in the world, the saola is so elusive that no biologist has ever observed one in the wild. The critically endangered species was photographed via a camera trap in Vietnam in 2013, which was the first time the ‘Asian unicorn’ had been seen there in the wild for 15 years, the Daily Mail reported. The saola wasn’t even discovered as a species until 1992, the first to be added to the scientific roster of large mammals in more than 50 years, according to the World Wildlife Fund.