News Release

Fossil poop infested with parasites from over 200 million years ago

Ancient predator was infected by nematodes and multiple other parasite species

Peer-Reviewed Publication


First discovery of parasite eggs in a vertebrate coprolite of the Late Triassic in Thailand

image: Coprolites collected in Nong Yakong village, Chaiyaphum Province, Thailand. view more 

Credit: Nonsrirach et al., CC-BY 4.0 (

Fossilized feces preserve evidence of ancient parasites that infected an aquatic predator over 200 million years ago, according to a study published August 9, 2023 in the open-access journal PLOS ONE by Thanit Nonsrirach of Mahasarakham University, Thailand and colleagues.

Parasites are a common and important component of ecosystems, but ancient parasites are difficult to study due to a poor fossil record. Parasites often inhabit the soft tissues of their host, which rarely preserve as fossils. There are, however, cases where traces of parasites can be identified within fossilized feces (coprolites). In this study, Nonsrirach and colleagues describe evidence of parasites in a Late Triassic coprolite from the Huai Hin Lat Formation of Thailand, which is over 200 million years old.

The coprolite is cylindrical in shape and over 7cm long. Based on its shape and contents, the researchers suggest it was likely produced by some species of phytosaur, crocodile-like predators which are also known from this fossil locality. Microscopic analysis of thin sections of the coprolite revealed six small, round, organic structures between 50-150 micrometers long. One of these, an oval-shaped structure with a thick shell, is identified as the egg of a parasitic nematode worm, while the others appear to represent additional worm eggs or protozoan cysts of unclear identity.

This is the first record of parasites in a terrestrial vertebrate host from the Late Triassic of Asia, and a rare glimpse into the life of an ancient animal that was apparently infected by multiple parasitic species. This discovery also adds to the few known examples of nematode eggs preserved within the coprolites of Mesozoic animals. These findings are therefore a significant contribution to scientific understanding of the distribution and ecology of parasites of the distant past.

The authors add: “Coprolite is a significant paleontological treasure trove, containing several undiscovered fossils and expanding our understanding of ancient ecosystems and food chains.”


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Citation: Nonsrirach T, Morand S, Ribas A, Manitkoon S, Lauprasert K, Claude J (2023) First discovery of parasite eggs in a vertebrate coprolite of the Late Triassic in Thailand. PLoS ONE 18(8): e0287891.

Author Countries: Thailand, Spain

Funding: This research project was financially supported by Mahasarakham University, by the IRN paleobiodivASE CNRS, by the Hubert Curien PHC project trophic network evolution of the Mesozoic of Thailand and its impact on biodiversity (2016-2017) and by the French Agence nationale de la recherche (project ANR-11-CEPL-0002 BiodivHealthSEA). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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