Saola

Saola were first discovered in 1992 by Vietnamese biologist, Do Tuoc.

An excerpt from the article 20 facts about saola
The discovery was officially announced by WWF on July 17th, 1992. It was not a living animal, however, that was discovered, but a horned skull. Since its traits differed significantly from any other known wild cattle species in Asia, it was assumed a new species.