Top predators ate and excreted their own young.
300 million years ago, a group of sharks called Orthacanthus held the status of top predators in the freshwater coastal swamps around Europe and North America. These creatures were nearly 10 feet (3 meters) in length and pierced their prey with unusual three-cusped teeth.
The tooth of Orthacanthus in oral view. Credit: Aodhán Ó Gogáin (Trinity College Dublin)
Their normal diet consisted of other fish species and amphibians, but between meals, these sharks were snacking on their own young, according to a study published in the journal Palaeontology,
The evidence comes from fossilized poop, called coprolites, which the researchers discovered in the Minto Coalfield in New Brunswick, Canada. "As palaeontologists cannot observe predator-prey relationships directly in the way that a zoologist can, they have to use other methods to interpret ancient food webs,” said study co-author Mike Benton, from the University of Bristol, in a press release.
The spiral shape of the poop helped the researchers determine that Orthacanthus, with its characteristics corkscrew-shaped rectum, had excreted it.
But more interesting than its shape were its contents. The fossilized feces were packed with baby teeth, also belonging to Orthacanthus, meaning these sharks has cannibalistic tendencies.
Study co-author Howard Falcon-Lang, from the Royal Holloway University of London, is uncertain why these sharks were cannibalizing their own young, but he suggests “Orthacanthus used inland waterways as protected nurseries to rear its babies, but then consumed them as food when other resources became scarce."
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