The shells are the first found at such a northerly latitude. The rich biodiversity of these fossils, which indicates that the dinosaurs weren’t just visiting but lived in the locale, refutes the competing theory of gradual decline from a variety of factors such as loss of habitat, introduction of predators, and appearance of disease — similar to the circumstances of many amphibians today. This lack of evidence for a long, slow decline is, according to the theory, a positive sign that there was, instead of a decline, a swift extinction. But it’s hardly conclusive. The odd geographical position of the site makes the fossil find fertile ground for argument on both sides of the rapid extinction debate. Accustomed to living at an average temperature of 50 degrees Fahrenheit, these cold-resistant species would have fared considerably better than tropical dinosaurs if a meteor strike initiated global cooling, for instance; so the rapid extinction theory does not provide a full accounting for their disappearance. Despite remaining mysteries, this surprising discovery of cold-dwelling dinosaurs who were not just surviving, but flourishing soon before a potential doomsday-meteor impact is making many paleontologists rethink the world of 66 million years ago. [Via Nature]
