【作者】 王念忠；

【Author】 Wang Nian-zhong;Institute of Vertebrate Palaeontology and Palaeoanthropology,Academia Sinica;

【机构】 中国科学院古脊椎动物与古人类研究所；

【摘要】 <正>潘江、刘运鹏1975年记述了湖北汉阳锅顶山的汉阳鱼(Hanyangaspis),认为它代表异甲鱼类的一个新目,并认为含鱼地层时代为早泥盆世。刘玉海(1979年)认为汉阳鱼不应该属于异甲鱼类,而应属于多鳃鱼类,并把汉阳鱼暂时作为多鳃鱼目中一未定属。潘江1984年把汉阳鱼置于"真盔甲鱼纲",作为这一纲中的类群I,并把含鱼地层时代改为中志留世。本文基于新材料对汉阳鱼重新作了描述,特别是对汉阳鱼头胸部背甲作了详细记述并绘制了复原图;认为以修正后的汉阳鱼为代表的汉阳鱼目被置于广义的盔甲鱼亚纲比较合适;含鱼地层以归中志留世为宜。更多还原

【Abstract】 Based on the new remains,this paper makes comments on Hanyangaspis and Latirostraspis which are regarded as the plesiotypes,with an essential emendation to the original diagnosis of the genera.The emended Hanyangaspis,instead of being considered as a heterostracan(Pan et al.,1975) or a polybranchiaspid(Liu,1979) should be placed in an independent order,the emended Hanyangaspidida,which belong to the Galeaspida.Latirostraspis has been originally regarded as a polybranchiaspid without a most important character of the Galeaspida,the large nasohypophsial opening on the antero-dorsal side of the dorsal shield.But the author has found that Latirostratpis possesses really a nasohypophycial opening in the dorsal shield just like that of Hanyangaspis,and thinks that the relationship between Latirostraspis and Hanyangaspis is much closer than that between either of them and any of the other known galeaspid genera.The emended diagnosis of Hangangaspidida may be given as floows:Dorsal side of cephalo-thoracic part covered by a single dorsal shield and bended toward ventral side,forming a cyclic ventral rim.Ortital openings lateral,separated far from each other;nasohypophysial opening very large,ellipselike in form;pineal opening small,situated behind the nasohypophysial opening.System of sensory canals including the X-shaped longitudinal lateral canals and short trasversal lateral canals,with two median-dorsal commissures parallel to each other.Oralo-branchial cavity covered by an anteroventral plate and a ventral plate.Crescent-shaped oral opening located at the rostro-ventral margin of the bead;several external branchial openings situated between cyclic ventral rim and ventral plate.Ornamentation consisting of snowf lake-like tubercles.Remarks:The emended Hanyangaspidida differs greatly from the typical forms of Galeaspida,Eugaleaspiformes and Polybranchiaspidormes in the distributional mode of sensory canals in the dorsal shield,the very large nasohypophysial opening,the form of oral opening,particularly in the form of oral branchial cavity.The age of the fish-bearing horizon,instead of being regarded as the Early Devonian for Hanyangaspis and the Late Silurian for Latirostraspis,should undoubtedly belong to the Middle Silurian based on the stratigraphical control which is mostly provided by the trilobites(Coronocephalus rex,Kailia sp.and Latiproetus sp.) and the brachiopods(Nalivkinia sp.and Nikiforovaena sp.).更多还原