It is not dinosaur skin. I thought it looked like a flattened tooth & consulted with our vertebrate paleontologist. He agrees with me that it is sufficiently distorted that he is not certain that it is organic – it might be a pseudo fossil created by inorganic means. If (and as my colleague said, it is a big if) this is a tooth, then it is o a part of a tooth of a large mammal. One way to potentially resolve this is - was this "unique" in the area where it was picked up? If so, a tooth seems most likely. If there were a lot of pieces that looked like this on the ground where this was picked up, it is much more likely it was created by an a-biological process, perhaps the drying out of a gel-like sedimentary substance.