BEEN BUSY FOR QUITE AWHILE, EH? (via Tom Corcoran):

'Jurassic beaver' found in China (BBC, 2/28/06)

The discovery of a beaver-like fossil that lived when the dinosaurs ruled the Earth could challenge some currently accepted ideas on mammal evolution.

Castorocauda lutrasimilis, which was unearthed in China, is a species previously unknown to science. [...]

The fossil was found in the Middle Jurassic Jiulongshan Formation, a deposit rich in the remains of dinosaurs, early insects and other organisms.

The creature had fur, a broad scaly tail, and webbed feet for swimming. It was about the size of a small female platypus and had seal-like teeth for eating fish.

Castorocauda lutrasimilis resembled a modern-day beaver, but belonged to a group that became extinct long before rodents appeared.