We got an early start didn't we:
The remarkable fossil bones of a fur-covered, swimming mammal that lived in the age of the dinosaurs 164 million years ago have been discovered in China, raising a wave of excitement among scientists whose timetable for mammalian evolution has just been pushed back by 100 million years (San Francisco Chronicle).
It makes you wonder how far back the evolution of mammals began. How many species lived in the time of the dinosaurs, and how many survived? This makes the imagination run wild. A lot of great fossils have been found in China lately.