Ok, it's not the crab pictured above for copyright reasons, but the Afzelius’s crab (Afrithelphusa afzelii) was last seen in 1796.
For those counting, that's about 225 years ago. AKA, no one alive knew what it really looked like.
Yet Mvogo Ndongo was determined to find it anyways. A trip to Sierra Leone and some help from the locals led Ndongo to a farm on the edge of a forest.
Intense searching took place, and... the crab was discovered!