Some days, it must not have been easy to be a hadrosaur. You're a dinosaur, sure, but it's hard to feel like a badass when your head resembles a duck. On the plus side, these herbivores outlasted more fashionable dinos such as the T-Rex in one respect: They had longer-lasting skin.
Indeed a preponderance of dinosaur skin samples (not actual skin, of course, but fossilized impressions) belong to hadrosaurs. Matt Davis, a fifth-year graduate student in paleontology at Yale University, has suggested a new reason why that might be the case. He proposes in a paper that hadrosaur skin endured because it must have been tougher texturally -- built to last long enough to write itself into the fossil record.
First, some backstory. Typical explanations for all of the hadrosaur skin left behind center around population and habitat. Hadrosaurs were all over the place in dinosaur times, and therefore, the idea goes, they simply left behind more skin for 21st-century paleontologists to ponder. Furthermore, hadrosaurs usually lived along rivers, where they could die in flash floods, their skin preserved in soil sediment unreachable by scavengers.
"If you are a hadrosaur versus another dinosaur, you're 31 times more likely to preserve skin," said Davis in a press release. He would know: To firm up the notion of hadrosaur skin prevalence, Davis reviewed published reports about dinosaur skin all the way back to 1841, to get a fix on how often skin samples were those of hadrosaurs as opposed to other dinosaurs.
Across 180 reports, Davis found that 46 percent of body fossils that had skin (not just trace fossil skin from something like footprints) belonged to hadrosaurs.
Next Davis looked at data from 343 dinosaurs found in the Hell Creek Formation in the Dakotas and Montana and at similar dino-rich formations in the United States and Canada. There, the hadrosaur skin fossil prevalence was overwhelming. Of the 22 Hell Creek dinosaurs that were kind enough to deposit traces of skin for future study, 20 came from hadrosaurs -- a whopping 91 percent.
"We've always assumed hadrosaur fossils preserved more skin," said Davis. "Now we've got the data to prove just how much more."
As for the population density and habitat arguments for why hadrosaur skin was so abundant, Davis counters that dinosaurs such as ceratopsians were even more common than hadrosaurs, yet far less skin from those creatures has been found, and hadrosaur skin has been discovered in environments other than just river valleys that could preserve skin fossils.
Davis said more more research needs to be done now, to figure out just how hadrosaur skin was tougher and thicker -- which exact characteristics made it so.
Why all the fuss about skin in the first place? While most dinosaur evidence comes in the form of fossilized bones, skin excels as a means for distinguishing among species and can help scientists work out the location and size of muscles as well as tell them more about how dinosaurs moved, where they lived, and how they looked.
Davis's research appears in the September 10 issue of the journal Acta Paleontologica Polonica.