1. Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, PO Box 643 , Beijing 100044, China
2. Department of Biological Sciences, Kean University, Union, New Jersey 07083, USA
3. URA12, Laboratoire de Palontologie, Musum National d'Histoire Naturelle, 8 rue Buffon, 75005 Paris, France

Correspondence to: Min Zhu¹ Correspondence and requests for materials should be addressed to M.Z. (e-mail: Email: zhumin@ht.rol.cn.net).

Living gnathostomes (jawed vertebrates) include chondrichthyans (sharks, rays and chimaeras) and osteichthyans or bony fishes. Living osteichthyans are divided into two lineages, namely actinopterygians (bichirs, sturgeons, gars, bowfins and teleosts) and sarcopterygians (coelacanths, lungfishes and tetrapods). It remains unclear how the two osteichthyan lineages acquired their respective characters and how their common osteichthyan ancestor arose from non-osteichthyan gnathostome groups¹, ². Here we present the first tentative reconstruction of a 400-million-year-old fossil fish from China (Fig. 1); this fossil fish combines features of sarcopterygians and actinopterygians and yet possesses large, paired fin spines previously found only in two extinct gnathostome groups (placoderms and acanthodians). This early bony fish provides a morphological link between osteichthyans and non-osteichthyan groups. It changes the polarity of many characters used at present in reconstructing osteichthyan inter-relationships and offers new insights into the origin and evolution of osteichthyans.