Non-avian dinosaurs may have been in decline before the asteroid impact, the asteroid just helped to finish them off.
http://news.softpedia.com/news/Dinosaur-...7345.shtml
http://www.sciencedaily.com/releases/201...134159.htm
http://news.softpedia.com/news/Dinosaur-...7345.shtml
http://www.sciencedaily.com/releases/201...134159.htm