On the horizon of Protopteryx and the early vertebrate fossil assemblages of the Jehol Biota Jin, Fan ; Zhang, FuCheng ; Li, ZhiHeng ; Zhang, JiangYong ; Li, Chun ; Zhou, ZhongHe Abstract Publication: Science Bulletin Pub Date: September 2008 DOI: 10.1007/s11434-008-0209-5 Bibcode: 2008SciBu..53.2820J