The zoomorphic images on Shang bronzes range from clearly mimetic low- or high-relief images of birds, snakes, crocodiles, and deer, to imaginary animals like dragons, and to highly stylized mask motifs that allude to animals but don't directly represent them. Since bronze vessels were used in sacrificial rituals, most observers assume the decoration symbolized something important in Shang political and religious cosmology. Unfortunately, texts that discuss the meaning of images exist only from much later periods.