Remarkable Dinosaur Mummy Has ‘Glittering’ Skin Gouged by Ancient Crocs

Remarkable Dinosaur Mummy Has ‘Glittering’ Skin Gouged by Ancient Crocs

Around 67 million years ago in what is now North Dakota, a duck-billed dinosaur keeled over and died, and crocodiles’ ancient relatives descended on the carcass, tearing holes through the skin and marking up the bones. The fossilized remains of the dino, which include amazing “mummified skin”, still show evidence of predators’ feast.

A new study suggests that these lingering bite marks could help explain how the dinosaur became an mummy. The research, published Wednesday (Oct. 12) in the journal PLOS One (opens in new tab), also proposes that dinosaur mummies with exceptionally well-preserved skin and soft tissues may be more common than scientists once thought.

“There was a common assumption that a rapid burial was necessary in order to obtain a mummy. This meant that the dinosaur would need to be buried as soon as possible after it dies, according to Stephanie Drumheller, coauthor of the study and a University of Tennessee, Knoxville palaeontologist. The remains of a dinosaur’s body would be protected from the elements and hungry scavengers if it was covered with sediment. This allowed the skin of the animal to mummify.

“Intuitively, if predators partially eat the remains, it can help the long-term stability of things like skin. Drumheller explained to Live Science that this can help with secondary chemical changes.

” It seems reasonable to me,” said Brian Pickles (an associate professor of ecology at University of Reading in the United Kingdom), who was not involved with the study. Pickles explained to Live Science that if the carcass was found on a riverbank or sandbar and there was nothing edible, then it is possible that the skin and bones were left there for a while. The skin would have dried in the sun before being covered up,” Pickles said in an email.

Full color Edmontosaurus reconstruction.
Full colour Edmontosaurus reconstruction by Natee Putapipat. Credit: Natee Puttapipat (CC-BY 4.0)

Drumheller and her colleagues drew these conclusions by examining a well-known Edmontosaurus fossil housed at the North Dakota Heritage Center and State Museum in Bismarck. The specimen, nicknamed “Dakota,” was discovered in 1999 on a ranch near Marmarth, in southwestern North Dakota. Specifically, it was excavated from the Hell Creek Formation, a fossil-packed geological formation that took shape near the end of the Cretaceous period (145 million to 66 million years ago) and the start of the Paleogene period (66 million to 23 million years ago).

The Edmontosaurus fossil is missing its head and the very tip of its tail, and it may also be missing its left forelimb, but the rest of the animal’s bones are intact, co-lead author Clint Boyd, senior paleontologist for the North Dakota Geological Survey, told Live Science. Large swathes of preserved skin cover the bones of the dinosaur’s right hind limbs, tail, and forelimb.

” The skin is a deep brown, almost blackish brown. It actually has a little shine to it, because it has so many iron in it,” said Mindy Householder, co-author of the study and a fossil preparator at the State Historical Society of North Dakota, Bismarck. She said that it almost looks like it’s shining.

Dakota’s glittering skin went on public display at the Heritage Center starting in 2014, although at that time, the fossil had not been completely freed of the rock surrounding it. In 2018, fossil preparators set about cleaning the specimen more thoroughly, and in that process, they uncovered markings that looked suspiciously like bite marks. Becky Barnes, a paleontologist and North Dakota Geological Survey lab manager, identified potential bite marks on the specimen’s tail. Householder discovered more on the right forelimb’s “pinky finger”.

Bite markings left on bones can fossilize very clearly. The team began searching for such marks and found distinct imprints on Dakota’s bone. Drumheller stated that finding bite marks in skin is more difficult. Skin can tear and stretch as it is bitten into and decomposition can further damage the tissue. The team used forensic studies of human and modern mammals to get an idea of the possible bite marks on dinosaur skin.

( Drumheller pointed out that although dinosaur skin is thicker than human skin, it’s still not a perfect match. )

The researchers discovered that Dakota’s “deep, raking furrows, and punctures” were likely caused by teeth or claws dragging flesh through. It’s possible that a crocodilian or a dinosaur, such as a large deinonychosaur or a juvenile Tyrannosaurus rex, may have left such marks, the study authors suggested. The study authors also noted more than a dozen puncture wounds found on Dakota’s right forelimb and right hand. They also noted that the skin of the former had been partially removed, possibly while a predator was feeding.

These injuries suggest that Dakota’s remains were not buried and are still susceptible to scavenging. But, if the dinosaur wasn’t quickly buried, how then did it mummify. The researchers again turned to forensic literature to find answers. They discovered a method of decomposition that could have been used by Dakota and other mummified dinosaurs.

This mummification process, which study authors call “desiccation & deflation,” could have allowed the dinosaur carcass to remain unburied for weeks, or even months, as animals, insects, and microbes to rip through the skin and eat away at the animal’s internal organs.

Any gasses or fluids from decomposition would have escaped through the skin’s gaps, allowing the skin to dry out completely.

The study indicates that the carcass would then have a “deflated appearance” with skin and dermal structures covering the bone. The dino would have been buried and fully fossilized later. It would look exactly like the mummified Dakota specimen.

” This is something that’s actually quite predictable in the forensic literature,” Drumheller stated. Drumheller stated that it was not something that had been considered in the context of dinosaurs mummies .”

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Not all dinosaur mummies are formed by desiccation or deflation, the authors emphasized, but it is reasonable to believe that most do. The study also suggested that other dino mummies may have been formed by rapid burial. However, others could have formed by being submerged in deep waters with very little oxygen. The lack of oxygen in the deep water would slow the decomposition process, enabling mummification to unfold, which is a process that has been documented in so-called bog bodies–swamp-preserved remains of medieval humans.

The researchers are confident that they know what happened between Dakota’s death and burial. However, details about what happened after burial remain unclear. The team plans to investigate which chemical reactions allow dinosaur skin to fossilize in this setting. They also plan to analyze more dinosaur skulls that most likely formed in the same manner as Dakota.

Pickles also said that there is still a mystery as to why so many fossilized dinosaur skins have been found. Pickles said, “If it were just predators and scavengers that leave skin behind on highly abundant herbivores then wouldn’t we expect lots of ceratopsian or sauropod fossils also with skin on them?” This is another question that we will explore in future studies.

While that research is underway, dinosaur enthusiasts can visit Dakota’s right foot, left forelimb and tail at the North Dakota Heritage Center or State Museum, Boyd stated. The remainder of the specimen is still being cleaned up and examined. Fossil preparators have spent about 14,000 hours working on Dakota so far, and they expect to spend several thousand more hours with the remarkable mummy before their work is done.

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    Nicoletta Lanese is a staff writer for Live

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