Paleontologists have found several species of parasites, including Ascaridida eggs, in a 200-million-year-old coprolite probably produced by a crocodile-like reptile and possibly a phytosaur.
Parasites found in the vertebrate coprolite from Thailand. Image credit: Nonsrirach et al., 10.1371/journal.pone.0287891.
“Paleoparasitology is the investigation of parasites found in paleontological and archaeological sites,” said Mahasarakham University researcher Thanit Nonsrirach and colleagues.
“Although specialized parasites producing traces in hard tissues have sometimes been partly identified, other parasites have a very poor fossil record because the soft tissues of the host in which they occur are rarely preserved, except in exceptional conditions such as in amber.”
“Another important source of parasite remains are coprolites, i.e., fossilized fecal material, which can shed light on trophic chains.”
“Several reports have described parasite eggs in coprolites,” they added.
“The assignment of coprolites to a specific host is challenging, but their different shapes can provide systematic information.”
“The insights into parasite-host interactions derived from these discoveries allow a better understanding of paleo-coevolution and paleo-ecosystems.”
“Helminth eggs have been described in vertebrate coprolites, including those of Permian sharks, cynodonts, dinosaurs and other Mesozoic archosaurs, and Quaternary mammals, e.g., hyena, deer and sloth.”
Life reconstruction of a phytosaur species called Protome batalaria. Image credit: Smokeybjb / CC BY-SA 3.0.
In their new study, the paleontologists examined a Late Triassic vertebrate coprolite from Thailand.
The specimen was collected by a Thai-French joint paleontological field survey in 2010 during a field work in the Huai Nam Aun outcrop near Nong Yakong village in the Thai province of Chaiyaphum.
It has an elongated cylindrical shape, curved on one side, with a rounded end, and is 7.4 cm in length and 2.1 cm in diameter. The surface is hard, smooth and gray in color.
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 terrestrial vertebrate hosts from the Late Triassic in Asia,” the authors said.
“It provides new information on parasite-host interactions during the Mesozoic era.”
The study is published in the journal PLoS ONE.
_____
T. Nonsrirach et al. 2023. First discovery of parasite eggs in a vertebrate coprolite of the Late Triassic in Thailand. PLoS ONE 18 (8): e0287891; doi: 10.1371/journal.pone.0287891
