The Yixian Formation of northeastern China has yielded important new fossil
s that are fuelling debates on the origin of angiosperms, on the early radi
ation of birds and of mammals, and on the origin of feathers, Although thes
e fossils provide a wealth of detailed anatomical information, knowledge of
the absolute age of the Yixian Formation is crucial if we are to understan
d their true evolutionary significance. The age of the Yixian Formation has
been disputed, but recent evidence provides strong support for an Early Cr
etaceous rather than a Late Jurassic age.