After reading the abstract, it sounds very interesting. I do have one big question: Do the remains show any difference from similar specimens prior to the K-T boundary? When you have small, isolated populations, you tend to get rapid evolution to suit the species to that specific area. If this small group of animals survived in an isolated fashion, I'd expect some sort of physiological drift from the mainline in order to compensate for their unique area.
If they don't show much difference, I have to wonder what, if anything, this says about the K-T event itself; whether it created a long-term climatological change in addition to a catastrophic change evidenced by the K-T geologic boundary. I'm also intrigued by the fact that these specimens were found in Colorado/New Mexico, which is pretty darn close to the best impact site candidate. I'd expect any animals that survived to be much further away.