Though not nearly as common as the bone fragments and bits of tooth found at dinosaur fossil sites, remnants and impressions of dinosaur skin are not as rare as you might think. Paleontologists have been finding them for more than a century. The delicate fossil traces are often easy to miss—fossil hunters may even unintentionally destroy them in the process of excavating a skeleton or bone—but paleontologists have slowly been accumulating a collection of dinosaur skin traces. The newest specimens, reported by scientists John Foster and Rebecca Hunt-Foster in the new issue of the Journal of Vertebrate Paleontology, come from the Jurassic rock of Colorado’s Morrison Formation.

Foster and Hunt-Foster describe three distinct skin specimens. Two of them are thin, carbonized patches of fossilized skin that appear to have come from sauropod dinosaurs. Both were found near sauropod bones. The third specimen, however, is not attributed to any particular dinosaur. The pebbly texture of the fossil skin identifies it as coming from a dinosaur, but the paleontologists leave its assignment as “indeterminate.”

Determining exactly what species of dinosaur the skin impressions represent is extremely difficult. There were a number of possibly candidates at the approximately 153-million-year-old site. Called the Mygatt-Moore Quarry, the locality has yielded the remains of the sauropods Apatosaurus, Camarasaurus and Diplodocus; the predatory dinosaurs Allosaurus and Ceratosaurus; the ankylosaur Mymoorapelta; and the small herbivore Othnielosaurus. The putative sauropod skin patches were found near Apatosaurus bones, making this famous dinosaur a good candidate for the pair of specimens.

Curiously, though, the Mygatt-Moore Quarry is not the only site of its kind to preserve thin, carbonized films of dinosaur skin. Two other Jurassic localities—the Howe Quarry in Wyoming and the Mother’s Day Quarry in Montana—have yielded similar specimens. Exactly why this is so is a mystery. Perhaps, Foster and Hunt-Foster hypothesize, the skin fossils were preserved due to a combination of factors including the thickness of dinosaur skin and the characteristics of the local environment. The details of the plant fossils at the site and the fact that the specimens are embedded in mudstone are consistent with a wet environment in which the skin of dead dinosaurs may have become naturally tanned due to the action of bacteria and acidic conditions. Dinosaur skin may have been more likely to be preserved under such a scenario, although, frustratingly, paleontologists are typically left with only scraps.

References:

Foster, J., & Hunt-Foster, R. (2011). New occurrences of dinosaur skin of two types (Sauropoda? and Dinosauria indet.) from the Late Jurassic of North America (Mygatt-Moore Quarry, Morrison Formation) Journal of Vertebrate Paleontology, 31 (3), 717-721 DOI: 10.1080/02724634.2011.557419