There is more than one way to mummify a dinosaur, according to a study

There is more than one way to mummify a dinosaur, according to a study
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Enlarge / Reconstruction of life in full color Edmontosaurus.

There is rarely time to write about every cool science story that comes our way. So this year, once again, we’re publishing a special series of posts on the Twelve Days of Christmas, highlighting an overlooked science story in 2022, each day from December 25 through January 5. Today: Why dinosaur “mummies” might not be as rare as scientists thought.

Under specific conditions, dinosaur fossils can include exceptionally well-preserved skin, something long thought to be rare. But the authors of a october paper published in the journal PLoS ONE suggested that these dinosaur “mummies” might be more common than previously believed, based on their analysis of a mummified duck-billed hadrosaur with well-preserved skin that showed unusual telltale signs of carrion in the form of carrion. bite marks. .

In this case, the term “mummy” refers to fossils that have well-preserved skin and sometimes other soft tissue. as we have previously reported, most fossils are bones, 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 a lot about aspects of the biology, ecology, and evolution of organisms so ancient that skeletons alone cannot convey.

For example, last year, researchers created a highly detailed 3D model of a 365 million year old ammonite fossil from the Jurassic combining advanced imaging techniques, revealing internal muscles that had never been observed before. Another team of British researchers experiments performed to look at involved dead sea bass carcasses 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 the dinosaur mummies, there is an ongoing debate over what appears to be a central contradiction. The dinosaur mummies discovered so far show signs of two different mummification processes. One is rapid burial, in which the body is quickly covered and further decomposition is slowed down substantially and the remains are protected from scavengers. The other common pathway is desiccation, which requires the body to remain exposed to the landscape for a period of time before burial.

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

There was evidence of multiple cuts and punctures on the forelimb and tail, as well as holes and scratches on the arm, hand bones, and arcuate-shaped skin, much like the shape of crocodile teeth. There were also longer V-shaped cuts on the tail that could have been made by a larger carnivorous predator, such as a juvenile. youyrannosaurus rex.

Proposed soft tissue preservation pathway based on the specimen studied.
Enlarge / Proposed soft tissue preservation pathway based on the specimen studied.

Becky Barnes/Plos ONE

The authors concluded that there is likely more than one path to dinosaur mummification, setting up the debate in a way that does not “require a spectacularly improbable convergence of events.” 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 seen in other dinosaur mummies and is also well documented in modern forensic studies. The authors believe that Dakota was “mummified” through a process called “dessiccation and deflation,” which involves incomplete harvesting, in which animal carcasses are emptied while scavengers and decomposers target internal tissues, Leaving behind skin and bones. By David Bressan in ForbesThis is what probably happened to Dakota:

After the animal died, its body was probably pillaged by a group of crocodiles, opening the carcass at the belly, and colonized by flies and beetles, cleaning the bones and skin of rotting meat. Such an incomplete sweep would have exposed the interior of the dermal tissue, after which the outer layers slowly dried. The underlying bones would keep the empty helmet from shrinking too much, preserving the finer details of the scaly skin. Eventually, the now mummified remains were buried under mud, perhaps by a sudden flash flood, and circulating fluids deposited minerals, replacing the remaining soft tissue and preserving a cast in the rock.

“Not only has the Dakota taught us that durable soft tissues, such as skin, can be preserved in partially removed carcasses, but these soft tissues can also provide a unique source of information about the other animals that interacted with a carcass after destruction.” death”. said co-author Clint Boydpaleontologist with the North Dakota Geological Survey.

DOI: PLoS ONE, 2022. 10.1371/daily.pone.0275240 (About DOIs).

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