Camel Canyon, just off the San Pedro River, has produced a number of fossils of mammals that lived here in Arizona about 5 million years ago. The fossils found include bears, stabbing (saber-toothed) cats, mastodons, horses, two kinds of camels, and llamas.
Another locality on the San Pedro River just across the County line in Pima County had all the same animals plus another type of stabbing cat, wolves, dogs, wolverines, and other smaller animals.
Many other unusual animals have been found as fossils in different parts of Arizona. They were certainly also present in Pinal County, but have not been preserved here. Animals like saber-toothed cats, lions, rhinoceros, and gomphotheres no doubt roamed the county during the last 66 million years (the Cenozoic Era).