Figure 20.19 Two Solutions to a Single Problem (A) This stingray, whose ancestors were dorsoventrally flattened, lies on its belly. Stingrays’ bodies are symmetrical around the dorsal backbone. (B) The flounder, whose ancestors were laterally flattened, lies on its side. (The backbone of this individual is at the left.) Flounders’ eyes migrate during development so that both are on the same side of the body.