200-Million-Year-Old Poop Reveals Parasites That Infected a Crocodile-Like Reptile

The prehistoric fossil could help researchers understand the relationships between parasites and host organisms in the Late Triassic

A person is crouching in front of a display of fossilized poops and reaching towards them with their hand
Fossilized poop, called coprolites, collected in Nong Yakong village, Chaiyaphum Province, Thailand. Coprolites are an important source for studying ancient parasites. Nonsrirach et al. under CC-BY 4.0

Scientists have sliced open 200-million-year-old, fossilized poop—likely from a creature that resembled a crocodile—and discovered the animal had been infected with prehistoric parasites.

The remains, unearthed in Thailand, are the first record of parasites living in a land vertebrate in Asia during the Late Triassic period, which lasted from around 200 million to 230 million years ago, according to a new study published Wednesday in the journal PLOS One. The findings suggest that multiple-parasite infections were common by this time.

“This discovery is crucial for understanding the variety of parasites and how they interacted in ancient ecosystems,” Thanit Nonsrirach, first author of the study and a paleontologist at Mahasarakham University in Thailand, says to New Scientist’s Corryn Wetzel.

Fossilized poop, called coprolite, can provide scientists with clues about which animals lived in a place at a certain time. It can also indicate what an organism’s meals were, for example, and how the creature’s digestive system worked.

Coprolites are also an important way to study parasite remains. Parasites often occupy an animal’s soft tissues, but those are rarely preserved in the fossil record. Instead, scientists look to prehistoric poop to learn about what may have infected animals long ago.

“Surprisingly, coprolites often contain fossils rarely preserved elsewhere,” Martin Qvarnström, a paleontologist at Uppsala University in Sweden who was not involved in the research, tells CNN’s Mindy Weisberger. “These include muscle cells, beautifully preserved insects, hair and parasite remains. But despite being treasure chests in this regard, coprolites are opaque, so identifying their inclusions can be challenging.”

The fossilized poop examined in the study was discovered during field work in 2010 near the Nong Yakong village in Thailand’s Chaiyaphum Province. It had a long and cylindrical shape, measuring about 2.9 inches long and 0.8 inches across. The coprolite’s surface was hard, smooth and gray. To analyze the fossil, researchers cut it into slices and inspected it under a microscope.

The poop contained what appeared to be eggs from at least six individual parasites of at least five different types. The researchers think one of the specimens belongs to an order of roundworm called Ascaridida due to its characteristic ovular shape and thick wall. They were unable to identify the other types of parasites, though they likely are protozoa and eggs of other worms.

“We were very surprised by the discovery of the parasite fossil,” Nonsrirach tells Inverse’s Elana Spivack. “Parasite fossils are quite rare, especially those from soft-bodied organisms.”

As for what animal created the coprolite, the researchers say it was probably a crocodile-like reptile, such as a phytosaur. The poop’s cylindrical, curved shape and the fact that it didn’t contain remains of prey are indicative of one of these creatures, per the paper. Adding to the evidence, tooth and bone remains from phytosaurs have been found in the same area as the poop.

Phytosaurs looked a lot like living crocodiles and seem to have gone extinct at the end of the Triassic. Despite their similar appearances, crocodiles and phytosaurs are not closely related—they simply developed similar features while evolving separately, according to the University of California Museum of Paleontology.

Whatever animal hosted these parasites, it would have acquired them by eating fish, amphibians or other reptiles that were infected. But merely carrying the parasites might not have made the animal sick. “Parasites have the ability to use their host as a way of development without causing disease to the host animal,” Nonsrirach tells CNN.

The findings provide insights into the relationships between parasites and hosts millions of years ago, the authors write.

“This new point of view gives us a deeper understanding of how past ecosystems were connected and how they affected the lives of prehistoric animals,” Nonsrirach tells Inverse.

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