Hyphalosaurus lingyuanensis,a major part of the Jehol Biota, this pice is very special actually, we can find no fossilized  bones, but the eye and skin could be identified. the darker side also clearly shows the ribs. the tail is very strong, and the tail skin mark shows the alligator-tail- like scale structure. found in Hebei Provence, China; Jehol Biota, Yixian formation;J3-K1 #fossil