A diademed sifaka (Propithecus diadema diadema) in Mantadia National Park, eastern Madagascar. It is one of the most beautiful lemurs. Lemurs belong to a group of primates called the prosimians, meaning before monkeys . Everywhere in the world except Madagascar, monkeys replaced them 35 million years ago. Madagascar has outstanding biodiversity; most of its flora and fauna is unique to the island and can be found nowhere else.