A study has found that there is more than one way to mummify a dinosaur

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

Under certain circumstances, dinosaur fossils can include exceptionally well-preserved skin—something long thought to be rare. But my authors October paper The publication 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 drosaur with well-preserved skin that showed unusual telltale signs of scavenging in the form of bite marks.

In this case, the term “mummy” refers to fossils with well-preserved skin and sometimes other soft tissues. as we are I mentioned earlierMost fossils are bones, shells, teeth, and other forms of “hard” tissue, but rare fossils are occasionally discovered that preserve soft tissues such as skin, muscles, organs, or even the occasional eyeball. This can tell scientists a great deal about aspects of the biology, ecology, and evolution of such ancient organisms that skeletons alone cannot move.

For example, last year, Create researchers Highly detailed 3D model of a 365-million-year-old ammonite fossil Jurassic period by combining advanced imaging techniques, revealing the internal muscles that have not been noticed before. Another team of British researchers Experiments were done That involved watching dead seabass carcasses rot to learn more about how (and why) the soft tissues of internal organs could 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. The dinosaur mummies discovered so far show signs of two different mummification processes. The first is rapid burial, where the body is quickly covered and the process of advanced decomposition is greatly slowed and the remains are protected from exhumation. Another common path is dehydration, 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, was discovered in the Hell Creek Formation in southwestern North Dakota and is now part of the North Dakota fossil collection. Nicknamed “Dakota,” this mummified dinosaur showed evidence of a quick burial and dehydration. The remains have been studied using various tools and techniques since 2008. The authors of the PLoS ONE paper also conducted a cross-sectional scan of the mummy, along with a grain size analysis of the surrounding sediment in which the fossil was found.

There was evidence of multiple cuts and punctures on the front and tail, as well as holes and scratches on the arm and hand bones and skin in the shape of an arc, much like the shape of a crocodile’s teeth. There were also longer V-shaped cuts on the tail that could have been caused by a larger carnivorous predator, such as juveniles. ttyrannosaurus rex.

The authors concluded that there was likely more than one route to mummification of the dinosaurs, settling the controversy in a way that did not “require an astonishing improbable convergence of events”. In short, more dinosaur remains may be mummified than previously thought.

In the case of Dakota, the shrunken appearance of the skin over the underlying bones has been observed in other dinosaur mummies, and has also been well documented in recent forensic studies. The authors believe the Dakota was “mummified” through a process called “desiccation and shrinkage,” which involves incomplete scavenging, where animal carcasses are emptied as scavenger and decomposer tools target the inner tissues, leaving behind skin and bone. Pier David Bressan at ForbesThis is what most likely happened to Dakota:

After the death of the animal, its body was probably scavenged by a group of crocodiles, the carcass opened in its stomach, and colonized by flies and beetles, to clean the bones and skin of the rotting flesh. Such an incomplete scavenging would have exposed the inner tissues of the skin, after which the outer layers would slowly become dry. The underlying bones prevent the empty shell from shrinking too much, preserving the fine details of the scaly skin. Finally, the now-mummified remains were buried under mud, possibly by a sudden flash flood, and circulating fluids laid out the minerals, replacing the remaining soft tissues and maintaining a mold in the rock.

“Not only did Dakota teach us that durable soft tissues such as skin can be preserved on partially bruised cadavers, but that these soft tissues can also provide a unique source of information about other animals that interacted with the corpse after death,” said co-author Clint Boyda paleontologist with the North Dakota Geological Survey.

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