See also: http://www.newscientist.com/article/dn10773-fossils-reveal-new-zealands-indigenous-mouse.html
Ancient Kiwi ‘mouse’ fills fossil gap
Lower jawbone of primitive ‘mouse’
(Image: PNAS/Worthy et al)
“Palaeontologists have found remains of one of the most primitive type of land mammal in the world, a mouse-sized creature that’s unlike any mammal alive today.
The find, at the edge of a swampy lake on New Zealand’s South Island, not only fills a gap of the nation’s fossil record, it may also help us understand more about the origin of mammals worldwide.”