I'd say the closest earth analog to them are probably penguins. Flightless, wings have adaptive specialization (in penguins fins, in rappies, they have little psudohands/claws at the end) and have a sort of upright posture where the mass of the body is over their legs as opposed to more "horizontal" body orientation like say an emu or an ostrich(for lack of a better way of putting it, i'm sure there's some official biological term for it)