鄂尔多斯地台南缘中奥陶统树形笔石群

鄂尔多斯地台南缘（陶西中部耀县，陇县４个地点）中奥陶统树形笔石，是一个新发现的区域性较强的底栖为主的树形笔石动物群，包括Ｄｅｎｄｒｏｉｄｅａ目中的Ｄｉｃｔｙｏｎｅｍａ，Ｄｅｎｄｒｏｇｒａｐｔｕｓ，ｐｔｉｌｏｇｒａｐｔｕｓ，Ａｃａｎｔｈｏｇｒａｐｔｕｓ，Ｔｈａｌｌｏｇｒａｐｔｕｓ，Ｍｅｄｕｓａｅｇｒａｐｔｕｓ属和Ｔｕｂｏｉｄｅａ目中的Ｇａｌｅｏｇｒａｐｔｕｓ属等２目７属１５种（含６新种）。共生的双笔

A STUDY OF DENDROID GRAPTOLITE FAUNA (MIDDLE ORDOVICIAN)FROM SOUTHERN BORDER OF ORDOS PLATFORM

The dendroid graptolites of China have been studied for more than five decades. Many important species of the genera Dictyonema, Desmograptus, Callograptus, Dendrograptus and Acanthograptus have been described by Professors Y. C. Sun. T. H. Yin, Singwu C.Hsu. A. T. Mu and other researchers. All these dendroids have been found from different localities of China. ranging from Upper Cambrian to Lower Carboniferous. mostly collected and described from the Upper Cambrian and Lower Ordovician. The Middle Ordovician dendroids were previously less known in China. A. T. Mu (].955) first described 3 species of them in his monograph entitled "The New Materials of the Dendroid Graptolites of China', namely Dictyonema szechuanense Mu. Ptilograptus glameratus var. sinicus Mu from Huayingshan of Sichuan and Dictyonema sp. C. from Meitan of Guizhou. Later, the present riter (1984) collected and described some new materials of the genus Medusaegraptus from the central Shaanxi region, while Zhao Yu--ting (1985) noted the dendroid graptolite Dendrograptus yangtzensis Mu from the Pingliang Formation of Pingliang, Gansu. Recently, Xiao and Zhong (1988) reported from Shiqian, uizhou 5 species, i. e., Dictyonema sp.C Mu, Dendrograptus of. yini Mu, Airograptus sp., canthograptus shiquanensis Xiao et hong and Nephelograptus gigateus Xiao et Zhong.