According to various press reports and news releases, there is a major new paper out in PNAS proposing that the pleistocene megafauna of North America (mammoths and the like) was killed off by an impact event (or atmospheric detonation of a comet). There was a brief report on this awhile ago when a paper was presented at the American Geophysical Union meeting this summer. This is a cool idea. However, despite the press announcements I can’t find the paper on the PNAS website. Anyone have any luck?