Study results show there is more than one way to mummify a dinosaur

Under certain conditions, dinosaur fossils can contain exceptionally well-preserved skin—an occurrence long thought to be rare. But the authors one October newspaper published in the journal PLoS ONE suggested that these dinosaur “mummies” may be more common than previously thought, based on their analysis of a mummified duckbill hadrosaur with well-preserved skin showing unusual telltale signs of scavengers in the form of bite marks had .

In this case, the term “mummy” refers to fossils with well-preserved skin and sometimes other soft tissue. As we’ve previously reported, most fossils are bone, shells, teeth, and other forms of “hard” tissue, but rare fossils are occasionally discovered that preserve soft tissue such as skin, muscle, organs, or even the occasional eyeball. This can tell scientists much about aspects of the biology, ecology, and evolution of such ancient organisms that skeletons alone cannot convey.

For example, last year researchers obtained a highly detailed 3D model of a 365-million-year-old ammonite fossil from the law Period through the combination of advanced imaging methods, reveals inner muscles this had never been observed before. Another team of British researchers conducted experiments observing the carcasses of dead sea bass rotting to learn more about how (and why) the soft tissues of internal organs can be selectively preserved in the fossil record.

In the case of dinosaur mummies, there is an ongoing debate over what appears to be a central contradiction. The dino mummies discovered so far show evidence of two distinct mummification processes. One of them is rapid burial, in which the body is quickly covered and advanced decomposition is slowed down significantly, protecting the remains from the scavenger. The other common route is desiccation, which requires the body to remain exposed to the landscape for some time before burial.

The specimen in question is the partial skeleton of Edmontosaurus, a duck-billed hadrosaur discovered in the Hell Creek Formation of southwestern North Dakota and is now part of the North Dakota State Fossil Collection. Named “Dakota,” this mummified dinosaur showed signs of both rapid burial and dehydration. The remains have been examined using various tools and techniques since 2008. The authors of the PLoS ONE paper also performed CT scans of the mummy, along with a grain size analysis of the surrounding sediments where the fossil was found.

There was evidence of multiple cuts and punctures on the front legs and tail, as well as holes and scratches on the arm, hand bones, and skin in the shape of an arc, similar to the shape of crocodile teeth. There were also longer V-shaped lacerations on the tail that could have come from a larger carnivorous predator, such as a juvenile TTyrannosaurus Rex.

Concluding that there is likely more than one way to mummify dinosaurs, the authors settled the debate so that “no spectacularly improbable convergence of events is required.” In short, dinosaur remains could be mummified more often than previously thought.

In the case of Dakota, the deflated appearance of the skin over the underlying bones has been observed in other dino mummies and is also well documented in modern forensic studies. The authors believe Dakota was “mummified” through a process called “desiccation and deflation,” in which animal carcasses are emptied while scavengers and decomposers target internal tissues, leaving skin and bones behind. Per David Bressan at Forbesthis is what probably happened with Dakota:

After the animal died, its body was likely eaten by a mob of crocodiles, the carcass opened at the belly and colonized by flies and beetles, which cleaned the bones and skin of the rotting flesh. Such incomplete cleansing would have exposed the skin tissue inside, after which the outer layers would slowly dry out. The underlying bones would prevent the empty shell from shrinking too much, preserving the finer details of the scaly skin. Eventually, the now-mummified remains were buried under mud, possibly by a sudden torrent, and circulating fluids deposited minerals, replacing the remaining soft tissue, and preserving a cast in the rock.

“Dakota not only taught us that permanent soft tissues like skin can be preserved on partially eaten carcasses, but these soft tissues can also provide a unique source of information about the other animals that have interacted with a carcass after death.” said co-author Clint Boyda paleontologist at the North Dakota Geological Survey.

DOI: PLoSONE, 2022. 10.1371/journal.pone.0275240 (About DOIs).

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