The finding discovered in 1985 in Turkana , Kenya , KNM WT 17000 ( known as the `` Black Skull '' due to the dark coloration of the bone , caused by high levels of manganese ) , is one of the earliest examples of robust hominids from Pliocene . The finding discovered in 1985 by Alan Walker in West Turkana , Kenya , KNM WT 17000 ( known as the `` Black Skull '' due to the dark coloration of the bone , caused by high levels of manganese ) , is one of the earliest examples of robust pliocene hominids .