Do birds come from dinosaurs, or could it be somewhat the other way around? the only way to completely and safely draw evolutionary trees is to recognize 'convergence' as Conway Morris does, to compare DNA, if possibly recoverable (recently happened in dinosaurs), and to follow biochemicals, again if recoverable. Morphology alone is a fooler:-http://www.sciencedaily.com/releases/2010/02/100209183335.htm