Mummified dinosaur has bite marks and gashes in its skin

An exceptionally well-preserved duck-billed hadrosaur found in North Dakota hints that dinosaur mummies may be more common than we think

Life 12 October 2022

Life reconstruction of Edmontosaurus

Illustration of the Edmontosaurus dinosaur and photograph of the preserved forelimb

Full color Edmontosaurus reconstruction by Natee Puttapipat, CC-BY 4.0

A 70-million-year-old dinosaur has preserved skin with gashes that suggest it was partially eaten by crocodile-like carnivores and possibly other animals – which may help explain why it became mummified.

As it was ripped apart, the estimated 7-metre-long duck-billed hadrosaur probably lost many of the bodily fluids and gases that promote decay, and then dried out before becoming buried under multiple layers of sediment.

Stephanie Drumheller-Horton at the University of Tennessee at Knoxville, a palaeontologist specialising in crocodile bites, was contacted by Clint Boyd at North Dakota Geological Survey in Bismarck to investigate the mummified remains of an Edmontosaurus dinosaur, found at the Hell Creek Formation of south-west North Dakota.

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The fossil was exceptionally well-preserved, with multiple gashes and punctures in the forelimb and tail. The arc-shaped series of holes and scrapes on the arm and hand bones and skin were almost certainly made by crocodile-like teeth grabbing on to the hadrosaur, she says. A set of longer, V-shaped gashes in the skin – especially along the once-meaty tail – could have been made by the claws of a much larger carnivore, possibly a juvenile Tyrannosaurus rex.

“Certainly whatever it was, the damage on the tail was physically larger than whatever was working on the arm,” says Drumheller-Horton. “So we think we have at least two different animals involved, and potentially more.”

The attacks probably emptied the cadaver in a way that slows decay – a phenomenon already known in forensic analysis of modern specimens. “So instead of all of that stuff sticking around inside the body, keeping it wet, pushing that decomposition along, it’s now out of the way,” says Drumheller-Horton. “It’s basically hollowed out and able to dry out, and what you have left behind is skin and bones.

“In honour of Halloween, I’ve been jokingly calling it a skeleton in a skin bag,” she says.

Even so, injury marks in soft tissue, like skin, don’t necessarily hold their original shape, which makes it more difficult to identify what happened, she says. The team is unsure whether the hadrosaur was attacked by predators before death or by scavengers after death – or both.

The findings overturn the notion that dinosaur mummies only occur in exceptional circumstances of very rapid burial or sudden drying, says Drumheller-Horton. They also suggest that mummification isn’t as rare as previously thought, as many partially eaten dinosaurs probably dried out before becoming buried under layers of sediment.

It is more likely that when scientists come across mummified dinosaur skin – which is extremely thin and fragile – they either mistake it for a simple imprint, or they never see it because it is accidentally destroyed as the fossil is removed from the sediment.

Journal reference: PLoS One, DOI: 10.1371/journal.pone.0275240

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