That is why I was curious. The Morrison is chock full of dinosaurs esp in Montana area. I just did not think it extended that far to AZ. I have been in this area and so much is sandstone, I did not see a great deal of preservation potential.
Nope wrong age. My mistake. It does appear in the area (or at least its equivalent), but is upper Jurassic. I am guessing these were found in the Dakota. And this is a SWAG.
Most Cretaceous sandstones are of marine origin. Terrestrial dinosaur fossil-bearing strata are usually siltstones, mudstones, fossilized volcanic ash, etc.