Stingrays are cartilaginous fish and live mostly on the sea floor. Their gills are on the bottom, or ventral side of their bodies and their eyes are on top. Their tail fins and dorsal fins are very small; on some species, they are absent altogether. Stingrays that lived about 100 million years ago have the same characteristics as those still alive today. In all that time, they have not undergone any changes. This suggests that evolution is an untenable theory.