The acanthothoracid Hagiangella goujeti Janvier, 2005, has been described exclusively on the basis of isolated thoracic plates from the Lochkovian (Lower Devonian) Khao Loc Formation of Tung Vai, Ha Giang Province, northern Vietnam. It is characterized by a very high, triangular median crest on the median dorsal plate, and has been referred to the Acanthothoraci on the basis of the morphology of its fused anterolateral, spinal and anterior ventrolateral plates, and the characteristic stellate ornamentation of the group. Isolated plates of H. goujeti are relatively abundant at Tung Vai and no other placoderm taxon from this locality seems to share the same type of ornamentation. However, the skull of this species remained elusive. Here we report two well-preserved skull roofs from Tung Vai, which we refer to H. goujeti. They display the same stellate ornamentation and small size as the previously described plates of the thoracic armor of this species. This new material shows that the head of H. goujeti is surprisingly short (i.e., possibly lacking dermal rostral and pineal elements), in contrast to the elongate and narrow skull of all other acanthothoracids. The combination of unique characters (e.g., presence of two pairs of posterior pit lines, two pairs of central and paranuchal plates, etc.) suggests a possible sister group relationship to the placoderm assemblage Petalichthyida Ptyctodontida Arthrodira.
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Vol. 31 • No. 3