Ancient parasite-infested fossil feces unearthed in Thailand

The ancient creature was probably infected by nematodes and other parasite species simultaneously.
Mrigakshi Dixit
Coprolites collected in Nong Yakong village, Chaiyaphum Province, Thailand.
Coprolites collected in Nong Yakong village, Chaiyaphum Province, Thailand.

Nonsrirach et al., CC-BY 4.0 

A well-preserved fossil record has the ability to provide little clues about a long-lost ancient world and its peculiar inhabitants.

Paleontologists have now unearthed rare evidence of ancient parasites that infected a predatory aquatic species over 200 million years ago. They found that the now-extinct predator was infected by nematodes (roundworms) and other parasite species simultaneously.

The evidence was found preserved in ancient fossilized excrement or coprolite of the animal, which was examined by Thailand's Mahasarakham University. 

The fossilized feces was recovered in Thailand's Huai Hin Lat Formation — dating back over 200 million years to the Late Triassic period. 

Finding evidence of million years old parasites is incredibly rare. This is because parasites mostly thrive on their host's soft tissues, which seldom survive as fossils. As a result, one of the options is to look for parasite traces in fossilized feces remains.  

Presence of various microscopic organisms

The newly-found fossilized coprolite exhibits a cylindrical shape and is almost seven centimeters long. 

After careful examination of its shape and composition, the team postulated that the excrement was most likely produced by a crocodile-like predator called a phytosaur. Paleontologists had previously discovered various individual remains of this species in the same area. 

Microscopic examination of thin slices of the coprolite revealed the presence of six tiny, spherical, organic entities ranging in size from 50 to 150 micrometers. 

“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,” described the official statement. 

The study offers a unique peek into the life of an ancient marine mammal that was probably infected at the time by various parasite species.  

Interestingly, this is the first fossil evidence of ancient parasites in a terrestrial vertebrate host from Asia's Late Triassic period. 

Furthermore, this discovery adds to the few known cases of nematode eggs preserved within Mesozoic animal coprolites. As a result, these findings provide important clues about the distribution and ecology of parasites in the ancient past.

And it could offer fresh insights into the parasite-host interactions that occurred millions of years ago. The authors add: “Coprolite is a significant paleontological treasure trove, containing several undiscovered fossils and expanding our understanding of ancient ecosystems and food chains.”

The findings were reported in the journal PLOS ONE. 

Study abstract:

A paleoparasitological investigation of a vertebrate coprolite from the Huai Hin Lat Formation (Upper Triassic) was carried out. Five morphotypes of potential parasite eggs or sporocysts were identified in the coprolite by microscopic analysis using thin section technique. The rounded or oval shape and thick shell of one of the five morphotypes suggests that it belongs to nematode of the order Ascaridida. Systematic assignment of other morphotypes cannot be done in detail but suggests that the host was parasitized by different species of parasites. This is the first record of parasites in terrestrial vertebrate hosts from the Late Triassic in Asia and it provides new information on parasite-host interactions during the Mesozoic era.

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