内蒙古大兴安岭乌奴耳地区泥盆纪的两个牙形刺动物群

TWO DEVONIAN CONODONT FAUNAS FROM ONOR AREA IN THE GREAT XING'AN RANGE OF INNER MONGOLIA,CHINA

在大兴安岭乌奴耳地区发现两个牙形刺动物群。一个采自北矿组,牙形刺Caudicriodus angulatus cf.cauda指示北矿组的时代为Eifelian早期。另一个样品采自霍博山组(大民山组)上部的角砾岩层,产有牙形刺的混合动物群。Palmatolepis hassi,Pal.ljashenkovae,Pal.kireevae,Pal.subrecta,Polygnathus decorosus,Icriodus ex-pansus,I.symmetricus等牙形刺主要来自Frasnian晚期晚rhenana带。而Ancyrodella binodosa,Ancyrodella nodosa,Schimitognathus cf.hermanni则主要来自Gevitian期晚期和Frasnian期早期;Ancyrognathus ubiquitus是重要的事件种,见于linguiformis带至早triangularis带(F/F界线层);这个角砾岩层最后形成的时代可能是早triangularis带,含有多层位的再沉积的牙形刺。文中共描述了牙形刺11属22种,包括2个未定新种和1个未定种。

Two conodont faunas have been found from Onor area in Inner Mongolia. One fauna contains Caudicriodus angustus cf. cauda,indicating that the Beikuang Formation should be early Eifelian in age. Another fauna yields many conodont specimens,including mainly Palmatolepis hassi,Pal. ljashenkovae,Pal. kireevae,Pal.subrecta,Polygnathus decorosus,Icriodus expansus,and I. symmetricus,indicating that this fauna is Frasnian,exactly late rhenana Zone. But latter fauna also contains early Frasnian conodonts （Ancyrodella binodosa,Ancyrodella nodosa and Schimitognathus cf. hermanni）,and a characteristic species of F/F boundary bed（Ancyrognathus ubiquitus）. It is possible that this is a mixed fauna,because the sample is collected from breccia flow deposits,containing reworked conodonts from different horizons. The age of the breccia bed could be early Famennian triangularis Zone,because Ancyrognathus ubiquitus is present in this fauna. It could be caused by tsunami that happened during the F/F event. Eleven conodont genura and 22 species are described in this paper,including two unnamed new species and an unnamed species.