A primitive sarcopterygian fish with an eyestalk

The discovery of two Early Devonian osteichthyan (bony fish) fossils(1-4) h as challenged established ideas about the origin of osteichthyans and their divergence into actinopterygians (teleosts and their relatives) and sarcop terygians (tetrapods, coelacanths, lungfishes and related groups)(5-7). Psa rolepis from China(1,2,8,9) and an unnamed braincase from Australia(3) comb ine derived sarcopterygian and actinopterygian characters with primitive fe atures previously restricted to non-osteichthyans, suggesting that early os teichthyan evolution may have involved substantial parallellism between sar copterygians and actinopterygians. But interpretation of these fossils has been hampered by poor phylogenetic resolution(1,3). Here we describe a basa l sarcopterygian fish, Achoania gen, et sp. nov., that fills the morphologi cal gap between Psarolepis and higher sarcoptergyians. We also report the p resence of eyestalk attachments in both Achoania and Psarolepis, showing th at this supposedly non-osteichthyan feature occurs in basal sarcopterygians as well as the actinoptergyian-like Australian braincase(3).