Tapeworm eggs found in 270-million-year-old fossilized shark feces provide the earliest known evidence of intestinal parasites in vertebrates.

A cluster of tapeworm eggs discovered in fossilized shark feces suggests that intestinal parasites in vertebrates are much older than previously known, according to a study published in the open access journal PLoS ONE.

Remains of such parasites in vertebrates from this era are rare – of 500 samples examined, only one revealed the tapeworm eggs.

This particular discovery helps establish a timeline for the evolution of present-day parasitic tapeworms that occur in foods like pork, fish and beef.

The fossilized eggs were found in a cluster very similar to those laid by modern tapeworms. Some of them are un-hatched and one contains what appears to be a developing larva.

“This discovery shows that the fossil record of vertebrate intestinal parasites is much older than was previously known and occurred at least 270-300 million years ago,” said Dr Paula Dentzien-Dias and colleagues from the Federal University of Rio Grande, Brazil.

The fossil is from Middle-Late Permian times, a period followed by the largest mass extinction known, when nearly 90 percent of marine species and 70 percent of terrestrial species died out.

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Bibliographic information: Dentzien-Dias PC et al. 2013. Tapeworm Eggs in a 270 Million-Year-Old Shark Coprolite. PLoS ONE 8(1): e55007; doi: 10.1371/journal.pone.0055007