Dinosaur reconstructions often begin and end with bones. Dinosaur muscles and organs usually don’t survive the processes that turn bodies into fossils, with casts of the intestinal tract–called cololites–and other soft tissue clues being rarities. Restoration of those squishy bits relies on comparison with modern animals, muscle scars on bones and other lines of evidence. Yet paleontologists have found a great deal of dinosaur skin impressions, especially from the shovel-beaked hadrosaurs of the Cretaceous. We probably know more about the actual external appearance of hadrosaurs such as Edmontosaurus and Saurolophus than almost any other dinosaurs.
Hadrosaurs found with skin impressions are often called “mummies.” This isn’t quite right. Natural mummies–human and otherwise–preserve the organism’s actual skin due to any number of environmental conditions, from arid heat to extreme cold or preservation in a bog. What we know of hadrosaur skin isn’t the original organic material that made up the dinosaur’s flesh, but rock that has made a mold or cast of the dinosaur’s pebbly outer coating. Terminology aside, though, paleontologists have found enough dinosaur skin impressions that the fossils can be used to detect different ornamentation patterns and may even help distinguish one species from another. Earlier this year, paleontologist Phil Bell demonstrated that two Saurolophus species exhibited different patterns on their bumpy skins–an additional kind of ornamentation aside from their prominent head crests.
But how do skin impressions became preserved? And why are such traces so often found with hadrosaurs but not other dinosaurs? Is it because hadrosaurs frequented environments where such preservation was more likely, or are we just missing similar impressions associated with other fossils? There’s much about dinosaur skin impressions that we don’t yet understand. In the video above, Bell gives us a preview of new research on a recently collected hadrosaur that has skin traces, in the hope that some high-tech analysis will help him better understand how such fossils form.