Data from fossils and modern carcasses indicates a simple path to preserving dinosaur skin.
Dinosaur “mummies” aren’t as exceptional as we might expect. That’s because of a relatively simple process of desiccation (drying out) and deflation, according to a study by Stephanie Drumheller of the University of Tennessee–Knoxville and colleagues that was published on October 12, 2022, in the open-access journal PLOS ONE.
The term “mummy” is often used to describe dinosaur fossils with fossilized skin. These are relatively rare. Many scientists believe that such fossils only form under exceptional circumstances. That’s because it is thought that in order for skin to become fossilized, a carcass must be shielded from scavenging and decomposition by rapid burial and/or desiccation. Drumheller and colleagues propose a novel explanation for how such “mummies” might form in this research study, where they combined insights from fossil evidence with observations on modern animal carcasses.
The investigators examined a fossil of a dinosaur called Edmontosaurus from North Dakota. It features large patches of desiccated and seemingly deflated skin on the limbs and tail. Bite marks from carnivores on the dinosaur’s skin were identified by the researchers. These are the first documented examples of unhealed carnivore damage on fossil dinosaur skin. Moreover, this is evidence that the dinosaur carcass was not protected from scavengers, yet it became a mummy nonetheless.
Illustrations on the left show incomplete predation and/or scavenging of the carcass creates openings in the body wall through which fluids and gasses can escape. Invertebrates and microbes use those openings to access the internal tissues. Removal of internal soft tissues and drainage of fluids and gasses associated with decomposition allows the deflated skin and other dermal tissues to desiccate and drape over the underlying bones. This process facilitates longer-term persistence of the skin and other resistant soft tissues until eventual burial and fossilization. Credit: Paleoart by Becky Barnes, CC-BY 4.0
Modern animal carcasses are known to be often emptied out, leaving behind skin and bone as scavengers and decomposers target internal tissues. The authors propose that damage to this dinosaur’s skin from this incomplete scavenging would have exposed its insides. This would have allowed a similar process to occur, after which the skin and bones became slowly desiccated and buried.
This process, which the authors call “desiccation and deflation,” is common with modern carcasses and explains how dinosaur mummies might form under relatively ordinary circumstances. However, the researchers stress that there are likely numerous pathways by which a dinosaur mummy might develop. 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 durable soft tissues like skin can be preserved on partially scavenged carcasses, but these soft tissues can also provide a unique source of information about the other animals that interacted with a carcass after death.”
Reference: ‘Biostratinomic alterations of an Edmontosaurus “mummy” reveal a pathway for soft tissue preservation without invoking “exceptional conditions”’ by Stephanie K. Drumheller, Clint A. Boyd, Becky M. S. Barnes and Mindy L. Householder, 12 October 2022, PLOS ONE.
DOI: 10.1371/journal.pone.0275240
