A NEW EARLY DEVONIAN GALEASPID FROM BAC THAI PROVINCE, VIETNAM

A new large galeaspid, Bannhuanaspis vukhuci gen. et sp. nov., is desc ribed from the top part of the Si Ka Formation or the base of the Bac Bun Formation (Early Devonian, Late Lochkovian or Early Pragian) in th e Phu Luong District, Bac Thai Province, northern Vietnam. The overall shape of its head shield is suggestive of the 'Polybranchiaspidiforme s', but this morphology is regarded as a primitive feature for the Gal easpida. Its transversely elongated median dorsal opening, broad poste rior margin of head shield and posterolaterally directed main lateral- line are also regarded as primitive galeaspid characteristics. However , it shares with the 'Polybranchiaspidiformes' and Huananaspidiformes a large number of gill openings, and with the Galeaspidiformes very sh ort and rounded cornual processes.