The brachial articulation and pectoral fin in antiarchs (placodermi)

The structure of the articulation for the pectoral fin in the Antiarchi is reviewed, with particular reference to the Early Devonian taxa from China, Vietnam and Australia: the Yunnanolepiformes, Procondylolepiformes and Sinolepidae. The Sinolepidae display an amazing diversity of structure of the brachial articulation area of the anterior ventrolateral plate, ranging from a very simple structure, like that of the Yunnanolepiformes, to more complex ones resembly quite closely that of the Euantiarchi. This suggests that the Sinolepidae may not be monophyletic, and that their presumed autapomorphy (the large ventral fenestration of the thoracic armour) could be either plesiomorphous for the Antiarchi or for the ensemble Sinolepidae + Euantiarchi, or also homoplastic in Vanchienolepis, Xichonolepis and Sinolepis. The pectoral fin exoskeleton is described in a Vanchienolepis-like specimen from Yunnan, and a possible pectoral fin, partly covered with scales or minute platelets is described in a specimen of Yunnanolepis from Vietnam.