Thing is, its speculation in the first place it was a meteor that wiped them out, well the majority, remember croc's and some other animals are still prehistoric in origin by barely evolving further over the past 60+ million years.
As always its best guess with the 'experts' in these area's we will never really know unless Einsteins theory of relativity, time travel and bending space, become reality and we can go back and see what really happened.
Until then, unless any real proof comes up, take it as a pinch of salt cos its most likely some young enthusiastic plonker trying to make a name for himself.