A paper in Nature disputes the significance of the KT boundary event:

I've been loving the combined ScienceBlogs feed over the past few weeks.

Along with the new io9 blog, these feeds continue to feed a longstanding love for both science and science fiction.

Take together, they provide a great mix of what is and what could be.

Today's reading brought me to to Greg Laden's blog, where he comments at length on a new paper published in Nature that disputes importance of the KT Boundary Event in mammalian evolution. (See the abstract for The delayed rise of present-day mammals for more; full access requires registration or a trip to the (gasp) library.)

As Laden says:

The KT boundary event is the moment in time when a ca. 10 km. diameter object going very fast hit the earth in the vicinity of the modern Yucatan, causing the extinction of the dinosaurs (and almost everything else larger than a microwave). It has been suggested that this event resulted in (allowed for) the subsequent diversification of the mammals, presumably because the earlier extinction event opened up previously filled niches, into which the mammals evolved, and possibly because of dramatic climate change that occurred with this event.

One of the reasons that this study is important is that it seems to falsify this long-standing hypothesis.

This paper is thoughtfully discussed on Pharyngula and Sandwalk, and I recommend that you have a look at those sites.

I suspect some of my more geologically-inclined friends will find this interesting as well. I'm glad to see that our understanding of evolutionary history continues to, well, evolve, based upon new research.