Good question! Turner 2012's paper on paravian systematics lists Microraptor as coming from both the Yixian and the Jiufotang. That's why it was included as such in my book. I had assumed further specimens from the Yixian were found and were among the ones discussed in Turner's paper. However, so far there doesn't seem to have been any more on this, and Turner does not cite any particular Yixian specimens. A few people have asked me about this and now that I think about it, I have a hunch Turner might have been including the Yixian specimen now known as Changyuraptor. Just a hunch, but it's possible. So far no other specific fossil currently assigned to Microraptor have been published as specifically hailing from the Yixian.