As an extension of our Mothers Day family outing, we went to an area I'd heard about that is reportedly a good place to find certain kinds of fossils. It is located on BLM land in Montana, but close to the Wyoming border and is near a couple of limestone mines. This area was once the bottom of a huge sea. I had a map someone had drawn for me, and we drove around and stopped and looked for quite some time without successfully finding anything like a fossil. There were no other people in the area. It was hot and it appeared to be rattlesnake territory.
Just as I was about ready to give it up, we came upon a couple of guys who were walking around looking at the ground and we were able to talk to them. They turned out to be a couple of scientists (biologists, actually, who are studying a horned lizard in the area). They were taking a break from their lizard study and were looking for gizzard stones. They had a couple in their packs and they showed us. I had heard of these gizzard stones, but had never seen them. Apparently, sauropod dinosaurs of the Cretaceous period swallowed stones to help them digest tough plant material. The stones got smooth over time and were spat out. They could be easily identified, because they were so different from the other rocks scattered about on the ground. We found some good specimens, pictured above. You can learn more about gizzard stones or gastroliths here.
I was also hoping to find some Belemnite fossils (Mesozoic squid), and the scientists told us where to go to find those as well as Gryphaea (oyster fossils) and fossilized corral. We followed their instructions, and did locate a huge deposit of the oyster shell fossils. The ground was literally littered with them. We looked for some time. We never did find any squid fossils and only one very small corral fossil.