迄今世界最早被子植物花序化石的首次发现

ON DEVONIAN LOCHKOVIAN AND FAMENNIAN CORAL FAUNAS

首次报道迄今已知世界最早的被子植物花序化石———Ｘｉｎｇｘｕｅｉｎａｈｅｉｌｏｎｇｊｉａｎｇｅｎｓｉｓｇｅｎ．ｅｔｓｐ．ｎｏｖ．。该花序化石产于我国黑龙江鸡西早白垩世城子河组。花序由数十枚小花组成，其花粉具典型的被子植物特征，无明确的萌发口器。根据其所在层位下伏海相层化石佐证，以及与以色列等地早期被子植物花粉化石的对比等，该花序的地质时代可能为早白垩世Ｈａｕｔｅｒｉｖｉａｎ晚期，或Ｈａｕｔｅｒｉｖｉａｎ晚期至Ｂａｒｅｍｉａｎ早期。文中还讨论了此花序及其花粉化石的发现在研究全球被子植物起源及早期演化等方面的重要意义。

There were less changes in the marine faunas at the Silurian Devonian boundary.The Lochkovian(earliest Devonian)corals are dominated by Silurian elements,but Pragian corals are dominated by early members of characteristic Devonian families.The Lochkovian Pragian boundary reflected the changeover from 'Silurian' to 'Devonian' dominance in the corals. The Lochkovian Carlinastraea coral fauna extended from China (Yunnan,Jilin and Inner Mongolia),Tadzhikistan (Zeravshan and Turkestan Ranges),Russia(Gornoy Altai,Salair and Urals),Czech(Bohemia),Canada(Yukon and British Columbia),U.S.A.(Alaska and Nevada) to Australia(New South Wales). The massive Carlinastraea fauna flourished in shallow water with sufficient oxgen,while the small solitary Syringaxon fauna lived possibly in slope,low energy and reductive environments. Most of the Devonian type corals became extinct at the end of the early Late Devonian(Frasnian).The Frasnian Famennian(F/F) extinction killed most platform dwelling corals;only a few genera of Frasnian shallow water corals survived this event. Very few corals are known from the Hsikuangshan Formation (lower Famennian) in central Hunan,South China.However,corals associated with brachiopods,conodonts ,cephalopods,trilobites,echinoderms and other fossils ,become abundant and diversified in the Hongguleleng Formation(lower Famennian) in northern Xinjiang,N.W.China.There was a perfect “refugium” , i.e.,a suitable living environment,for marine faunas at that time. A new Strunian(late Famennian) coral fauna has developed in the Shaodong and Mengkungao Formations in South China.This fauna falls into two communities:one is a shallow water community represented by the Cystophrentis fauna which lived in a nearshore region with rough sea water and sufficient oxygen ,and the other is an offshore community called the Cyathaxonia fauna which inhabited the slope region with quiet and stagnant sea water.The Cystophrentis fauna located in BA 3 of Boucot's Benthic Assemblage Scale has been regarded as the earliest Carboniferous coral zone in South China for a long time,while the Cyathaxonia fauna located in BA 5 of Boucot's Benthic Assemblage Scale fauna has a longer geological range. The Strunian faunas have no phylogenetical relation to known Late Devonian Frasnian corals but they are forerunners of Carboniferous ones.The Late Devonian coral faunas underwent three evolutionary stages known as the extinction stage,the survival stage and a recovery stage.Eventually,most Strunian corals became extinct at the Devonian Carboniferous boundary,with the appearance of another new Tournaisian type coral fauna in the earliest Carboniferous.