Oops. Sorry about the misspelling. But was the biped hopping? Or could have all the rightside peds have disappeared in a landslide--some kind of breakway of the land? Or perhaps it was some kind of primeval hopscotch? Or maybe another animal bit off the right leg of the biped and the poor thing was hopping off to its last rites. Or maybe its young had the right leg in its mouth, playing pull-away and the biped was trying to get away, hopping, of course, in the game. Or it could have been riding a scooter with its right foot up on the foothold with the left leg pushing along to propel it. Or maybe it had a right stump from a previous injury. Cats do that all the time and get around pretty well on three; an old biped lizard might be able to make it around on one.