So far, there are 3 species of giant lemurs identified in Madagascar, Palaeopropithecus kelyus, Palaeopropithecus ingens and Palaeopropithecus maximus. P. kelyus is the smallest of all three, its estimated weight is about 77 lbs. The largest living lemur in Madagascar is the Indri, which weighs about 22lbs. Judging from the teeth, P. kelyus might have chewed on tough food such as seeds and nuts.
Read about the article from LiveScience: New Giant Lemur Species Discovered.