Rare parasites found in 200 million-year-old reptile poop

Even ancient aquatic predators can't avoid the occasional pest.
A man is looking in a glass case of coprolites collected in Nong Yakong village, Chaiyaphum Province, Thailand.
Nonsrirach et al. CC-BY 4.0

What goes into the body, must ultimately come out.  The same goes for the parasites living within a host. The parasite-host relationship is also pretty old, and some newly found fossilized feces show the ancient parasites infected an aquatic predator more than 200 million years ago. The findings are published August 9 in the open-access journal PLOS ONE.

[Related: ‘Brainwashing’ parasites inherit a strange genetic gap.]

Despite being a common and important player in the food web due to their role in regulating overpopulation within the ecosystem, ancient parasites are difficult to study in the fossil record. They typically inhabit their host’s soft tissues, which are not usually preserved in fossils like tougher parts like bones. However, traces of parasites can sometimes be identified in fossilized feces which are called coprolites

“Coprolite is a significant paleontological treasure trove, containing several undiscovered fossils and expanding our understanding of ancient ecosystems and food chains,” the authors wrote in a statement.

In this study, the team describes evidence found in coprolite dating back to the Late Triassic from Thailand’s Huai Hin Lat Formation, which is over 200 million years old. The coprolite is shaped like a cylinder and more than 2.7 inches long. The team believes that it was likely produced by some species of a crocodile-like predator called a phytosaur based on the shape of the fossilized poop and the remains of phytosaurs have been found in the area for decades

Within the thin sections of coprolite, the team found six small, round, organic structures roughly between only 50 to 150 micrometers long. One of these microscopic beauties is an oval-shaped structure with a thick shell which the team identified as the egg of a parasitic nematode worm called Ascaridida. The other five structures possibly represent additional worm eggs or protozoan cysts. 

“The discovery of at least six parasites with at least five different morphotypes in a single coprolite suggests that multi-parasite infection was common had already diversified by the late

Triassic,” the authors wrote in the study

It is believed to be the first record of parasites in a terrestrial vertebrate host in Asia from the Late Triassic period, when the Earth was warmer and more humid than it is today. It also offers a glimpse into an ancient animal who was infected by multiple species of parasite as it went about its life. 

[Related: What prehistoric poop reveals about extinct giant animals.]

“The presence of the Ascaridida eggs and the evidence for multi-infection found in the coprolite can presumably be explained by the predatory habits of the host, which would have been parasitized by feeding on parasitized fishes, amphibians, or other reptiles,” they wrote.

This finding also adds to the few known examples of nematode eggs preserved within the fossilized poop in prehistoric animals and will add more understanding to how parasites were distributed on Earth millions of years ago.