Were dinosaurs dull green and grey like today’s large reptiles, or bright and flashy like their descendants, the birds? For a long time this was considered an unanswerable question, but that may soon change due to a singularly well-preserved sample of skin from a hadrosaur — a duck-billed dinosaur from the late Cretaceous — found near Grand Prairie, Alberta last summer. That sample is currently undergoing analysis at the Canadian Light Source (CLS), a particle accelerator based in Saskatoon, Saskatchewan. It turns out that the ultra-modern discipline of particle physics may be just the way to shed light — literally — on a hundred million-year-old mystery.
The fossil came from a remote area of northwestern Alberta known as the Wapiti formation. Due to the fact that there are relatively few places where erosion has exposed underlying rock, the Wapiti’s rich fossil reserves have thus far remained largely untapped. Paleontologist Philip Bell of the Pipestone Creek Dinosaur Initiative is among the few investigators who trawl the dry riverbeds each summer, looking to see if the spring runoff has exposed any fossils. In June of 2012, Bell’s team came upon a cliff that had collapsed to reveal bits of dinosaur material. “I first picked up a bit with skin impressions, and I thought, great, there should be more in there,” says Bell. “We immediately changed our approach to make sure everything was kept in pristine condition. Soon, we hit upon a section of skin that was glossy and black, unlike anything I had ever seen in the field before. We looked at it closely, and realized that it had a three-dimensional structure.” While skin impressions are not unheard of, only one or two examples of actual preserved skin samples from any dinosaur have ever been found.
Bell showed the sample to his collaborator Mauricio Barbi, a high-energy physicist at the University of Regina. Although physics may seem far removed paleontology, for Barbi the chance to do field work is the fulfillment of a childhood dream. He comes along to digs whenever he can, and he was just as excited by the skin as Bell. “I remember one of the technicians looking at us like we were crazy; we were laughing and talking about projects we could do with it,” says Barbi. One of the possibilities involves looking for melanosomes, small structures within cells that contain the pigment melanin. In recent years, paleontologists from Britain, China and the US have used scanning electron microscopes to analyse melanosomes found in preserved dinosaur feathers. By comparing their shape, size and distribution with those of modern birds, they’ve been able to make educated guesses about the colours of a few dinosaur species. Doing the same in skin would cross a new frontier. “It has never been done before,” says Barbi.
But before he starts looking for melanosomes, Barbi will leverage his knowledge of physics and the power of the Canadian Light Source to answer some much more fundamental questions. At CLS, powerful magnetic fields and microwave radiation are used to accelerate electrons to within a fraction of the speed of light, then suddenly shove them in a different direction. This change in momentum causes the electrons to give off intense beams of photons, light which can be used to probe the molecular and atomic content of samples, including dinosaur skin. “Depending on the wavelength that you use, you can see different things,” says Barbi. “You can take images, but also you can get information about the chemistry.”
One of Barbi’s techniques involves shining infrared light on the sample and detecting which frequencies are absorbed into the atomic bonds that make up its molecules. The technique — called infrared (IR) spectroscopy — allows Barbi to work out which chemical species are present in the fossil. For example, long-chain hydrocarbons might be left over from the breakdown of fats or oils in the skin. If he uses higher-energy light — x-rays for instance — Barbi can focus on individual atoms to find out precisely which elements are present: iron from blood, or calcium from bone. Techniques like these are commonly used in chemistry labs, but the ultra-bright, narrowly focused light from CLS allows Barbi to probe deeper into the sample, and to focus his attention on specific areas. “You can see differences between the skin, the bone and the surrounding sediment,” says Barbi. “You can map the sample down to the level of a micron.”
It will likely be months to years before the team has enough data to start speculating about the colours of dinosaur skin. But in the meantime, the experiments conducted at CLS can help answer other important questions, such as why this particular sample was so well-preserved. “Obviously skin is something that decays rapidly, so the fossilization must have been incredibly fast,” says Bell. “We suspect that in this case, bacteria and their by-products forced minerals to precipitate out from the surrounding environment before it had a chance to decompose.” If that’s true, it almost certainly means that many more samples of dino skin may be waiting in the cliffs near Grand Prairie. “We’re continually amazed at the discoveries that turn up,” says Bell. “I guess really it should come as no surprise when, in the future, someone is able to identify the colour in one of these animals.”
Philip Bell also happens to be the head paleontologist for Canada’s newest dinosaur museum, currently under construction and scheduled to open in 2014. Find out more about the project at curriemuseum.ca.