A large, blackish aquatic crake with prominent white bill and frontal shield. Looks tailless. Sootyblack head and neck with a more grey than black body and whitish trailing edge to wings. Sexes alike. Juvenile has whitish throat and foreneck, grey bill with no shield. Greenish feet. Feeds on vegetable matter. Flocks may panic and splatter clumsily across the water. Flies low but strongly, with lobed toes projecting. Builds anchored, floating reed nest.