Fossilized Poop Reveals 240 Million-Year-Old Parasite That Infected Mammal Ancestors

Scientists have discovered the most ancient pinworm to date. They uncovered an egg much smaller than a common grain of sand in a tiny piece of fossilized dung that shows that this parasite lived 240 million years ago.

The pinworm egg was discovered in a coprolite, which is fossilized feces, that was collected from an excavation site in Rio Grande do Sul state in southern Brazil. This site also held abundant fossilized remains of cynodonts, which are the ancestors of modern mammals.

The pinworm egg actually represents a new species. Now named Paleoxyuriscockburni, the structure of the pinworm egg placed it in a biological group of parasites that occur in animals that ingest large amounts of plant material.

This pinworm isn't just interesting in and of itself. It also can help determine the age of fossilized organisms and help establish dates of origin and diversification for association between host species and parasites. Coprolites, in particular, are a key part of the study of parasites in ancient animals. These fossils enable a better understanding of the ecological relationships between hosts and parasites.

"This discovery represents a first for our team, and I think it opens the door to finding additional parasites in other species of fossil organisms," said Scott Gardner, one of the researchers, in a news release.

The findings confirm that herbivorous cynodonts were infected with these parasitic nematodes. It also hints that it's likely that herbivorous dinosaurs also carried pinworms.

The findings are published in the journal Parasites & Vectors.

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