Might be Middle or Late Jurassic; this hinges on the age of the
Daohugou Bed.
Which is... drum roll... Early Cretaceous. It lies below the Yixian Fm, but
above the Tuchengzi Fm. A radiometric date from "the upper part" of the
latter is very close to the Berriasian-Valanginian boundary, so the Daohugou
Bed could be anything from Valanginian to Barremian in age. I posted on this
last summer.