From a ScienceNow article (subscription required):

The fossil record is chock-full of angiosperms, a testament to the extraordinary explosion of flowering plants that began around 140 million years ago. Today, angiosperms boast a diversity of 250,000 to 300,000 species, compared to 10,000 kinds of ferns… Most major lineages of polypod ferns, which comprise more than 80% of today’s fern species, arose and diversified a mere 100 million years ago, after the major riot of flowering plants… “The idea that the polypods took advantage of the angiosperms– that’s hot!” says David Barrington of the University of Vermont in Burlington.

In fact, one might call it the hotness if one were into California slang… scientists are fun and funny folk.