The Sierra Leone Crab is restricted to freshwater habitats in the Upper Guinea rainforest zone and known only from three crabs collected in 1955. Relatives of these crabs were recently rediscovered and have striking orange and purple coloration, an unusual inflated carapace and an unusual ecology—they climb trees! A search for this crab could also include a search for two other lost species in the Upper Guinea rainforest zone, Afzeli’s Crab (Afrithelphusa azfelli), which is known from two individuals collected before 1800, and Gerhilda’s Crab (Afrithelphusa gerhildae). All three species were likely lost because they live in obscure, out-of-the-way places such as trees, caves, mountain streams and cracks in rocks.

In 2021, Pierre A. Mvogo Ndongo, a lecturer and researcher, not only rediscovered the Sierra Leone crab (Afrithelphusa leonensis), but also found a species of freshwater crab lost to science since 1796, and discovered two crab species previously unknown to science. Photo by Pierre A. Mvogo Ndongo.