Parasites have a disturbingly deep history. Many of the sneaky little hitchhikers around today – from feather lice to fungi that control the behavior of ants – have been around for millions and millions of years. Tapeworms, amoebas, and their kind are some of evolution’s greatest success stories.

Finding ancient parasites is no easy task, though. The ancient critters are difficult to detect, and their discovery is often an accident. Nevertheless, a scattered record of prehistoric parasites is starting to come together, and the latest find may be the earliest known record of tapeworms infesting a vertebrate.

The fossil in question is a shark coprolite – feces that were buried on a lakebed 270 million years