Many dinosaurs are now considered to have been warm blooded. The Therapods in particular were a lot more like birds than reptiles. Not that any of this changes the fact that an asteroid hit the Earth at the time of their demise or anything ...
A whole lot more than dinosaurs died out 65M years ago, and there is physical evidence (Iridium) in the clay layer of the KT boundary around the globe. The combination of evidence, along with ranges of species dieoffs make asteroid impact the most likely culprit, even though some dino's may have already been on the decline due to other changes.
http://www.isgs.uiuc.edu/dinos/de_4/5c51d90.htm
Best Regards,