Analyzing coprolites—the preserved poop of people—is dirty, stinky work. But every once in a while, it reveals something truly surprising.

In the case of a new paper in the Journal of Archaeological Science, that startling something was the fang of a venomous snake, digested by a person and left in a rock shelter in what is now Texas about 1,500 years ago.

Archaeologist Elanor Sonderman, who found the fang as part of her graduate work at Texas A&M University, wasn’t looking for that particular needle in a haystack of prehistoric feces. Rather, she wanted to learn more about the indigenous people who used the Conejo Shelter, a cave in the Lower Pecos canyonlands of Texas, as a latrine. The shelter