The southern cassowary is the third biggest bird after the ostrich and emu. Compared to the single wattled northern cassowary, it is slightly larger and has two wattles, which hang loosely from its neck.
It resembles a dinosaur with its helmet-like spongy casque that grows throughout life. The casque may be used for pushing through undergrowth, regulating temperature, and detecting the calls of other cassowaries.