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. Department of Palaeontology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK

Correspondence to: Per E. Ahlberg³ Correspondence and requests for materials should be addressed to M.Z.

Abstract

The discovery of two Early Devonian osteichthyan (bony fish) fossils^{1, 2, 3, 4} has challenged established ideas about the origin of osteichthyans and their divergence into actinopterygians (teleosts and their relatives) and sarcopterygians (tetrapods, coelacanths, lungfishes and related groups)^{5, 6, 7}. Psarolepis from China^{1, 2, 8, 9} and an unnamed braincase from Australia³ combine derived sarcopterygian and actinopterygian characters with primitive features previously restricted to non-osteichthyans, suggesting that early osteichthyan evolution may have involved substantial parallellism between sarcopterygians and actinopterygians. But interpretation of these fossils has been hampered by poor phylogenetic resolution^{1, 3}. Here we describe a basal sarcopterygian fish, Achoania gen, et sp. nov., that fills the morphological gap between Psarolepis and higher sarcoptergyians. We also report the presence of eyestalk attachments in both Achoania and Psarolepis, showing that this supposedly non-osteichthyan feature occurs in basal sarcopterygians as well as the actinoptergyian-like Australian braincase³.