Coprolites, or fossilised faeces, collected in Thailand
Nonsrirach et al
Fossilised faeces of a crocodile-like predator living 200 million years ago show evidence of multiple parasite species. The discovery of ancient parasites is quite challenging, thus this finding provides valuable insights into their spread from one species to another.
Parasites primarily infect the soft tissues of animals, which are rarely preserved over time. Therefore, Thanit Nonsrirach and his colleagues from Mahasarakham University in Thailand examined a sample of fossilised dung, or coprolite, that was unearthed in 2010 from the Huai Hin Lat Formation in north-eastern Thailand.
“I wanted to investigate the contents of the coprolite, so I decided to cut it open and examine its internal structure,” says Nonsrirach.
The shape and contents of the faeces helped the researchers identify the creature it originated from. They initially photographed and measured the coprolite before stabilising it with an epoxy resin. Then, they sliced the log – 7 centimetres long and 2 centimetres thick – into thin sections resembling salami.
Upon examining the slides under a microscope, the team discovered a variety of parasite eggs trapped in the droppings. The eggs were mostly round and oval-shaped, comparable in thickness to a human hair. The team suspects that the coprolite contains as many as six parasite species, including intestinal worms known as nematodes from the order Ascaridida.
The researchers concluded that the excrement was most likely left by an armoured, semi-aquatic reptile resembling a modern crocodile. “Considering that crocodiles appeared around 100 million years ago during the Late Cretaceous, it is likely that the coprolite came from a crocodile-like animal or one that co-evolved with crocodiles, such as phytosaurs,” explains Nonsrirach.
Based on the remains of ancient plants and animals found in the same area, the researchers estimated that the specimen dates back to the early Late Triassic Epoch, approximately 237 million to 208 million years ago. “This discovery is crucial for understanding the diversity of parasites and how they interacted in ancient ecosystems,” adds Nonsrirach. He speculates that the animal ingested the parasites by feeding on infected fishes, amphibians, or other reptiles.
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