The origin of specimens like this one is disputed. Early scientific studies concluded that they were indeed fossilized droppings of a prehistoric animal, small lizard-sized reptiles or inland ancient turtles that wandered in what is now SW Washington 5 to 10 million years ago. After deposition the organic material was converted into iron carbonate over a period of thousands of years. Other scientists think they are intestinal casts (cololites). Others dispute those claims and state that they are pseudocoprolites or pseudofossils of volcanic origin. Personally, I tend to agree with the latter and think of them as "Earth poop." I believe they were squeezed out, just not by an animal!
My reasons for believing they have geologic rather than fecal (biological) origins is that no body fossils are present in the location these are found. If teeth, bone, and scales didn't survive the fossilization process, why would soft fecal matter survive?