I don’t have time to comment at the moment (perhaps over the weekend), but this looks interesting:
The big dinosaur extinction of 65 million years ago didn’t produce a flurry of new species in the ancestry of modern mammals after all, says a huge study that challenges a long-standing theory.
Scientists who constructed a massive evolutionary family tree for mammals found no sign of such a burst of new species at that time among the ancestors of present-day animals…
Instead, they showed an initial burst between 100 million about 85 million years ago, with another between about 55 million and 35 million year ago, researchers report in Thursday’s issue of the journal Nature.
The Nature paper is here.