About 70 million years ago, carnivores attacked a dead dinosaur – where the US state of North Dakota is located today. They eviscerated an Edmontosaurus, a herbivorous quadruped from the group of hadrosaurs. And although the predators had torn the dinosaur apart and eaten parts of it, fossilized parts of its skin. Paleontologists led by Stephanie Drumheller from the University of Tennessee-Knoxville, who examined the fossilized dinosaur skin, consider in the journal »PLOS ONE« whether the tissue of Cretaceous organisms has not survived millions of years more often than previously assumed, but has simply been overlooked so far.
The fossils from the Hell Creek Formation in North Dakota include several pieces of skin from the right foreleg of the Edmontosaurus, from the hind legs and from the tail. The fossilized parts are very well preserved, some of the horn substance has also been preserved, i.e. the toenails. The research group also discovered bite marks on the dinosaur's forelimb and tail. The experts attribute the tooth impressions to crocodile-like animals or a young Tyrannosaurus rex.
Because researchers assume that the fabric of living things is only preserved under very special conditions, it has not yet been surprised that very few such finds are available. Skin, for example, should only petrify when the primeval climate was particularly dry, the remains quickly covered by sediments and, if possible, were not dismantled by predators. However, these criteria only partially apply to the skin fossils from the Hell Creek formation. While the late chalk, when Edmontosaurus was stripped around in North Dakota, there was a forested bank area, i.e. a moist environment, at the site. The dead animal had also been torn down.
The team led by Drumheller therefore examined the skin parts prepared from the rock with the help of a computer tomograph. It turned out that the skin and bones of the dinosaur are preserved, but the muscle tissue is almost completely missing. The researchers suspect that – similar to animal carcasses today - the predators eat up their meat and enter microbes under the skin through the bite wounds and further decompose muscles and innards. The carcass was thus virtually hollowed out. In this way, the skin of the Edmontosaurus could have dried out and preserved itself more easily.
Since many living things were carnivore at the time, paleontologists would have to recover much more freely petrified tissue areas than is the case. However, because skin is comparatively thin, according to Drumheller and her team, it may often not be recognized as such when exposed.
