Some fossils are called "paired" fossils, when the layers containing a fossil are split open. As a result, the fossil has a positive, raised image on one side and a negative, concave "mold" on the other slab of stone. The 95-million-year-old catshark fossil in the picture is one such two-part specimen. Catshark belong to sharks classification. The catshark shown here belongs to the Scyliorhidinae family. Modern-day catshark are identical to those that lived 95 million years ago, which fact challenges the theory of evolution. This catshark fossil can be observed on both negative and positive plates.