The islands of São Tomé, Príncipe and their archipegalo, which lie in the Gulf of Guinea about 250km off the coast of Gabon, are likened to the Galápagos Islands for a very specific reason: like their Pacific cousins, which contributed to Charles Darwin's theory of evolution, these isolated volcanic islands have an incredible number of plant and animal species unique to them.

http://www.theafricareport.com/West-Africa/sao-tome-principe-a-taste-of-africas-galapagos.html