"Luruku" initiates took a year-long oath of silence and were taught a sign language known as "marlda kangka" (literally, ‘hand language’), which, though limited in its semantic scope, was fairly complex.Anthropologist David McKnight's research in the 1990s suggests that "marlda kangka" classifies animals somewhat differently from Lardil, having, for example, a class containing all shellfish (which Lardil lacks) and lacking an inclusive sign for ‘dugong+turtle’ (Lardil "dilmirrur").