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 These 300-million-year-old sharks ate their own babies and pooped them out in spirals

A new study suggests that Orthacanthus sharks turned to cannibalism when food became scarce, with evidence of baby shark teeth being found in poop fossils unearthed from an old Canadian coalfield.

“There is already evidence from fossilised stomach contents that ancient sharks like Orthacanthus preyed on amphibians and other fish, but this is the first evidence that these sharks also ate the young of their own species,” said palaeontologist Aodhán Ó Gogáin from Trinity College Dublin in Ireland.

Finding juvenile teeth in ancient shark poop wouldn’t have been enough on its own to suggest that Orthacanthus resorted to cannibalism when other food sources ran low. After all, it’s possible that some other carnivorous marine species was feeding on the baby sharks, and excreted the undigested teeth in their droppings.

But what most likely settles the identification issue is the shape of the fossil poop that the researchers found.