I suspect this caterpillar is closely related to similar looking nymphalid butterfly caterpillars in the genus Adelpha. Some are generally referred to as moss caterpillars because the various body projections give the appearance of moss. It may not be obvious from these photos, but check out this photo from Flickr user artour_a.
I’ve encountered a similar caterpillar before in a different part of Brazil, although that one was probably an earlier instar and was shades of brown.
by Jeffrey C. Miller, Daniel H. Janzen and Winifred Hallwachs