Loren Coleman gives the honor to Dr. Andrea Marshall, who discovered a huge and striking new species that had been (sometimes, anyway) in plain sight. No one before her had made much of a study of the manta populations off the coast of Africa. When Marshall looked at them thoroughly, she discovered they included two species, one coastal (this was the known species) and a larger, deeper-water denizen which could be distinguished by its more triangular fins, its lifestyle (migratory), and its sheer size (up to eight meters across and weighing up to two metric tons). Marshall did something important to all of science: looking at something no one else had examined and finding what no one else had noticed.
I nominated Debbie Martyr as runner-up for her rediscovery of the Sumatran muntjac and her continuing progress in solving the mystery of the orang-pendek - the likeliest, in my view, of all the cryptid primates to prove a new species.