The silky sifaka (Propithecus candidus), or silky simpona, is a large lemur characterized by long, silky, white fur. It has a very restricted range in northeastern Madagascar, where it is known locally as the simpona. It is one of the rarest mammals on Earth, and is listed by the International Union for Conservation of Nature (IUCN) as one of the world's 25 most critically endangered primates. The silky sifaka is one of nine sifaka species (genus Propithecus), and one of four former subspecies of diademed sifaka (P. diadema). Studies in 2004 and 2007 compared external proportions, genetics, and cranio-dental anatomy supporting full species status, which has generally been accepted.