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云南曲靖志留纪罗德洛世真盔甲鱼类一新属

2012年第50卷 第1期: 1-7

发表日期:2012-02-09来源:放大 缩小

编辑:朱敏,刘玉海,贾连涛,盖志琨

摘要:记述了云南曲靖潇湘区关底组(志留系罗德洛统)真盔甲鱼类一新属、新种——长孔盾鱼(Dunyu longiforus gen. et sp. nov.), 丰富了以梦幻鬼鱼为代表的潇湘脊椎动物群的组成。该新属具真盔甲鱼科的鉴别特征:后眶上管和中背管二者连续过渡,后端两侧辏合呈“U”字形,侧背管仅发出3条侧横管。新属内角缺如,这一特征过去在真盔甲鱼科中仅见于真盔甲鱼属。新属区别于真盔甲鱼属的主要特征有:角向后方延伸,呈棘状或叶状;头甲最宽处位于角末端之前,宽长比小于1.1; 中背孔末端超越眶孔后缘连线。基于对秀山真盔甲鱼头甲标本的重新观察,将秀山真盔甲鱼归入盾鱼属。新种区别于秀山盾鱼(Dunyu xiushanensis)的特征有:个体较大,头甲长大于宽;角呈棘状;眶孔位置相对靠前,头甲眶前区与眶后区的长度之比小于0.75; 多边形崮状瘤点,较大,长可超过2 mm。

关键词:云南曲靖,志留纪,盔甲鱼类,真盔甲鱼科,新属

卷期:50卷 01期

 

A new genus of eugaleaspidiforms (Agnatha: Galeaspida) from the Ludlow, Silurian of Qujing, Yunnan, southwestern China

 

ZHU Min, LIU Yu-hai. JIA Lian-tao, GAI Zhi-kun

 

Abstract  A new genus and species of the Eugaleaspidiformes (Agnatha: Galeaspida), Dunyu longiforus gen. et sp. nov., is described from the Ludlow (Silurian) Kuanti Formation of Qujing, Yunnan, southwestern China, in association with the oldest near-complete gnathostome Guiyu oneiros of the Xiaoxiang Vertebrate Fauna. The new genus is most suggestive of Eugaleaspis of the Eugaleaspidae by the absence of inner corners, in addition to the diagnostic features of the family, such as only 3 pairs of lateral transverse canals from lateral dorsal canals, and the U-shaped trajectory of median dorsal canals. They differ in that the new genus possesses a pair of posteriorly extending corners, the breadth/length ratio of the shield smaller than 1.1, and the posterior end of median dorsal opening beyond the posterior margin of orbits. Eugaleaspis xiushanensis from the Wenlock Huixingshao Formation of Chongqing is re-assigned to Dunyu, based on the new examination of the type specimen which shows a pair of posteriorly extending lobate corners and three (instead of four in the original description) pairs of lateral transverse canals. The new species differs from Dunyu xiushanensis in its large cephalic shield which is longer than broad, spine-shaped corners, anteriorly positioned orbits, the length ratio between preorbital and postorbital portions of the shield less than 0.75, and large polygonal, flat-topping tubercles exceeding 2.0 mm in length.

Key words  Qujing, Yunnan; Silurian; Galeaspida, Eugaleaspidiformes, new genus

 

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