Gliding squirrel from 125 mya found. This is bird territory. The NYTimes article aslo mentions a semi-aquatic pre-K/T find.
http://www.nytimes.com/2006/12/14/science/14mammal.html
http://news.independent.co.uk/world/science_technology/article2073054.ece
http://www.nytimes.com/2006/12/14/science/14mammal.html
http://news.independent.co.uk/world/science_technology/article2073054.ece