There’s more than one way to mummify a dinosaur, study finds

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There is rarely time to write about all the interesting science stories that come our way. So this year, we’re running a series of special Twelve Days of Christmas posts again, highlighting a science story that fell through the cracks in 2022, every day from December 25th to January 5th. Today: Why dinosaur “mummies” may not be as rare as scientists thought.

Under specific conditions, dinosaur fossils can include exceptionally well-preserved skin, a fact long thought to be rare. But the authors of an October paper 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 duck-billed hadrosaur with well-preserved skin that showed signs of unusual telltales of elimination in the form of bite marks. .

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

For example, last year, created researchers a highly detailed 3D model of a 365-million-year-old ammonite fossil from jurassic period combining advanced imaging techniques, revealing the internal muscles which had never been observed before. Another team of British researchers experiments performed which involved watching the carcasses of dead sea bass rot 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 about what appears to be a central contradiction. Dinosaur mummies discovered so far show signs of two different mummification processes. One is rapid burial, in which the body is quickly covered and advanced decomposition is substantially slowed and the remains are protected from litter. The other common route 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 of southwestern North Dakota and now part of the North Dakota State Fossil Collection. Named “Dakota,” this mummified dinosaur showed evidence of both rapid burial and desiccation. The remains have been studied 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 in which it was buried. find the fossil

There was evidence of multiple gashes and punctures on the forelimbs and tail, as well as holes and scratches on the arm, hand bones and skin in an arc, 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. TIrannosaurus rex.

The authors concluded that there is likely more than one route to dinosaur mummification, settling 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 Dakota’s case, 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 Dakota was “mummified” through a process called “desiccation and deflation,” which involves incomplete disposal, in which animal carcasses are emptied as scavengers and decomposers target the internal tissues, leaving back skin and bones. By David Bressan at ForbesHere’s what probably happened to Dakota:

After the animal’s death, its body was probably scavenged by a group of crocodiles, opening the carcass through its belly and colonized by flies and beetles, cleaning the bones and skin of the rotting flesh. This incomplete removal would have exposed the interior of the dermal tissue, after which the outer layers slowly desiccated. The underlying bones would prevent the hollow hull from shrinking too much, preserving the finer details of the scaly skin. Eventually, the now-mummified remains were buried under mud, perhaps by a flash flood, and circulating fluids deposited minerals, replacing the remaining soft tissue and preserving a mold in the rock.

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

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