中文摘要：

记述了云南昭通早泥盆世布拉格期坡松冲组华南鱼目一新属、新种——剑裂甲鱼（Rhegmaspisxiphoideagen．etsp．nov．）。新属的主要特征是：具有鱼雷形头甲，细长吻突，眶孔位于头甲腹侧位，鳃穴向头甲腹面弯曲，角、内角和腹环丢失。鉴于以上特征，新属被归到了包括鸭吻鱼和乌蒙山鱼在内的鸭吻鱼科。根据新材料提供的信息，修订了鸭吻鱼科，包括鸭吻鱼和乌蒙山鱼的鳃穴、腹环、角、内角等特征。裂甲鱼属是该地区发现的第一个具有流线形体型的盔甲鱼类，指示了该地区一些盔甲鱼类可能开始了一种营上底栖的生活方式，具有更加主动的取食行为。新属的发现不仅丰富了该地区华南鱼目的多样性，而且提供了盔甲鱼类在早泥盆世布拉格期通过占据新的生态位而发生的最后一次辐射演化的证据。

英文摘要：

A new genus and species of the Huananaspiformes （Galeaspida）, Rhegmaspis xiphoidea, is described from the Posongchong Formation （Pragian, Early Devonian）, Zhaotong, Yunnan Province, China. The new taxon is characterized by having a torpedo-shaped head- shield, a long rostral process, ventrolaterally set orbits, and ventrally curved branchial fossae, but no corners, inner corners, and ventral rim of head-shield. It is assigned to the family Gantarostrataspidae that include Gantarostrataspis and Wumengshanaspis. According to the new material and new observation, the Gantarostrataspidae is emended and a fresh look is prososed for Gantarostrataspis and Wumengshanaspis. As a streamlined jawless fish, Rhegmaspis displays an adaptation for a suprabenthic lifestyle with more active feeding behavior among galeaspids. The new form not only enriches the diversity of the Huananaspiformes, but also provides evidence for the last adaptive radiation of galeaspids by occupying an unexploited ecological niche during the Pragian of the Early Devonian.