中泥盆世盔甲鱼类在中国的首次发现

<正> 盔甲鱼类(galeaspids)为东亚区志留纪及泥盆纪分布很广的无颌类化石,但迄今为止,中泥盆世的盔甲鱼类还无确切记载。本文记述的盔甲鱼类不完整头甲,为广西区域地质调查队罗璋同志1975年所采,代表一新属种——近中显眶鱼Clarorbis apponomedianus gen. et sp. nov.,化石产于广西博白县三滩乡下六司一带的中泥盆世灰白色薄层至中厚层粉砂质泥岩中。1979及1987年,我们曾两次赴化石产地,仅获得一些盔甲鱼类碎片,同

FIRST DISCOVERY OF MIDDLE DEVONIAN GALEASPIDS IN CHINA

A new galeaspid genus, which has been excavated from Bobai, southeastern Guangxi, is described in the present paper. The fossil-bearing strata consist mainly of pale silty mudstone and greyish sandstone, yielding abundant fishes (Guangsipetalichthys bobaiensis, Bothriolepis sp., Hunanolepis tieni, sinolepids, sarcopterygians, etc.) and some invertebrates. According to the associated placoderms, the new galeaspid is regarded as Middle Devonian in age. It is the first convincing record of the Middle Devonian galeaspids in China, thus has an important biostratigraphic and biogeographic significance. Drder Polybranchiaspidida Genus Clarorbis gen. nov. Ciarorbis apponomedianus gen. et sp. nov. (Fig. 1; Plate Ⅰ) Derivation of Name Clar-(Latin), distinct; orbis (Latin), orbit; appono(Latin), place near; medianus (Latin), middle. Type An incomplete cephalic shield. Field No. 6003-12. Cat. No. GMV 2078. Locality and Horizon Santan, Bobai County, soutkeastern Guangxi; Middle Devonian. Diagnosis Large galeaspid of cephalic lateral margin similar to Polybranchiaspis or Dongfangaspis; Orbital opening round, 7mm in diameter and far from the cephalic lateral margin; Infraorbital canal near and around the orbital lateral side, meeting the anterior marginal and lateral dorsal canals at each end, and possessing five short lateral branches; Supraorbital canal V-shaped and meeting the anterior marginal canal in front of the orbital opening; Lateral dorsal canal far from the lateral margin of carapace; Head shield ornamented with the tiny crowded tubercles. Remarks Clarorbis gen. nov., beyond question, belongs to the Order Polybranchiaspidida because of its polybranchiaspid-typed sensory line system and V-shaped supraorbital canal. It differs from other galeaspids in the infraorbital canal with five lateral branches and in the orbital opening far from the cephalic lateral margin.