The further evolution of these early forms of heavy cavalry in Western Eurasia is not entirely clear. Heavily armored riders on large horses appear in 4th century BC frescoes in the northern Black Sea region, notably at a time when the Scythians, who relied on light horse archers, were superseded by the Sarmatians. By the 3rd century BC, light cavalry units were used in most eastern armies, but still only "relatively few states in the East or West attempted to imitate the Assyrian and Chorasmian experiments with mailed cavalry".