New information on the morphology of yunnanolepid antiarchs (Placoderm fishes) from the Early Devonian of South China

Abstract

ABSTRACT Skull morphology is described from acid-prepared articulated specimens of the antiarch Phymolepis cuifenshanensis from the Early Devonian of Yunnan Province, South China. The nasal and circum-orbital bones have a similar structure to the advanced antiarch Bothriolepis, but with the nasal openings bounded laterally by the sclerotic ring. Yunnanolepis parvus is reinterpreted to have the same structure, assumed primitive for antiarchs. The suborbital plates of Phymolepis meet in the midline, are crossed by a single sensory groove, and also carry possible cutaneous sensory pits as in arthrodires. Three bones (submarginal, prelateral, and infraprelateral) are identified in the cheek complex, and comparisons with Yunnanolepis suggest that they were also present in other primitive antiarchs. Traces of an opercular cartilage are described for the first time in an antiarch. The sensory canal pattern of Phymolepis differs from that of Yunnanolepis, with the supraorbital canal entering the preorbital depres...