A person on a thread here, wrote about going fossil hunting and finding some fossilized dinosaur poop. Coprolite, it's officially called.
Dang. Now that has me trying to remember an old sci-fi short story on the subject. I can't remember author, title, publication date or even year--- prior to 1980, I'm sure. But it involved time-traveling archeologists who did something to damage the existence of coprolite fossils, and one of the party volunteered to replace the missing source specimens, so-to-speak. She had to eat lots of roughage, and was no longer overweight at the end of the trip...