A primitive fossil fish sheds light on the origin of bony fishes

Living gnathostomes (jawed vertebrates) include chondrichthyans (sharks, ra ys and chimaeras) and osteichthyans or bony fishes. Living osteichthyans ar e divided into two lineages, namely actinopterygians (bichirs, sturgeons, g ars, 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 aros e from non-osteichthyan gnathostome groups(1,2), Here we present the first tentative reconstruction of a 400-million-year-old fossil fish from China ( Fig, 1); this foss:il fish combines features of sarcopterygians and actinop terygians 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-oste ichthyan groups. It changes the polarity of many characters used at present in reconstructing osteichthyan interrelationships and offers new insights into the origin and evolution of osteichthyans.