Dinosaur mummies may not be as uncommon as we think

A process of desiccation and deflation explains why dinosaur “mummies” are not as extraordinary as we might expect, according to a study published in the Open Access Journal on October 12, 2022 PLUS ONE by Stephanie Drumheller of the University of Tennessee-Knoxville and colleagues.

The term “mummy” is often used to describe dinosaur fossils with petrified skin, which are relatively rare. It is generally believed that such fossils only form under exceptional circumstances and that in order for the skin to petrify, a carcass must be protected from scavengers and decomposition by rapid burial and/or drying out. In this study, Drumheller and colleagues combine fossil evidence with observations on modern animal carcasses to propose a new explanation for how such “mummies” might have arisen.

The researchers examined a fossil of a dinosaur called Edmontosaurus from North Dakota, which has large patches of dried and apparently deflated skin on its limbs and tail. They identified carnivore bite marks on the dinosaur’s skin. These are the first examples of unhealed carnivore damage on fossil dinosaur skin, and moreover, this is evidence that the dinosaur carcass was not protected from scavengers but became a mummy nonetheless.

Modern animal carcasses are known to be dumped often, as scavengers and decomposers target internal tissues, leaving skin and bones behind. The authors suggest that damaging this dinosaur’s skin from this incomplete cleaning would have exposed its interior and allowed for a similar process, after which the skin and bones slowly dried out and were buried.

This process, which the authors call “desiccation and deflation,” is common in modern carcasses and explains how dinosaur mummies can form under relatively ordinary circumstances. The authors emphasize that there are likely numerous ways in which a dinosaur mummy could evolve. Understanding these mechanisms will guide how paleontologists collect and interpret such rare and informative fossils.

Clint Boyd, senior paleontologist at the North Dakota Geological Survey, adds, “Not only has Dakota taught us that permanent soft tissues, such as skin, can be preserved on partially eaten carcasses, but these soft tissues can provide a unique source of information about the other animals, who interacted with a carcass after death.”