| Precambrian,About 7/8 of the geological history,is an significant geological period in the history of the earth's evolution.In that stage,the earth has experienced the beginning of chaos,violent tectonic movement,to later stability,which is important to understand the early Marine environment,the formation of continents,the origin and evolution of organisms.Neoproterozoic(1000-541Ma),as the vital turning point between Phanerozoic and Cryptozoiceon,is a very important and unique time in the Precambrian period,and has been the focus of geologists.Typical geological events in this period include the formation and disintegration of Rodinia supercontinent,massive glacial development in low latitude,rapid oxygenation of the atmosphere and oceans.,and the origin and prosperity of macrosomal multicellular organisms.With the deepening of the research on the Edicaran biote,the organdifferentiated epigenetic biota,emergening in the later of Neoproterozoic,the understanding of its biological features,properties and ancient environment has been perfected.However,the study on the relatively simple macroalgae biota in the early period of stretching is relatively backward.Here,we focus on Longfenshan biota,including the simple planktonic Chuariaceae-Tawuiaceae and Longfengshaniaceae,which has the histological differentiation of thallus,phomopsis and holdfast,from Huailai,Hebei provinve,systematically summarizes previous research results,and select the typical Longfengshan section as the main serearch object to study the biological characteristics and its geological significance of the early simple macroalgae,at the same time,explore the structure and living environment of the organisms.The main gains as follows.1.More than 3000 pieces of Chuariaceae,Tawuiaceae,Longfengshaniaceae macroalgae of longfengshan biota,which was collected from the three sections of the esat slope,south slope and west slope of Huailai,Hebei province,were high precision Microscopic observation observed and statistically analyzed.The resualts are compared with previous researches and systematically summarized it,then determined the classification system of taxonomy of longfengshan biota,Chuariaceae includes Chuaria circularia,Beltanelloides cf.sorichevae.Tawuiaceae includes only Tawuia dalensis,and the short rod-like Nephyroformia,Phascolites,oval Shouhsienia,ligulifoem Glossophyton,oval Ovidiscina,sole-like Pumilibaxa,Shrug rods-like Tachymacrus are all synonym of Tawuia.When it comes to Longfengshaniaceae,the Morphological characteristics of Paralamilaria xinglongensis are unstable,cancle it and classified this kind of shape fossils as Longfengshania ellipticulum.because of the stem length is easily affected by the preservation of fossils and the characteristics is inteabilital,cancle L.longipetiolata,which can be belonged to L.ovalis.Two new morphological species were found,Longfengshaniafungorumis sp.nov.,Paralongfengshania longfurumis sp.nov.,then Longfengshanianceae includes 2 genus and 16 species.Two conformis were found,Suketea cf.rampuraensis,Beltanelloides cf.sorichevae.2.The system development characteristics of Longfengshaniaceae were analyzed by cluster analysis.It can be classifed into five types,I-simple basic type,including L.stipitata,L.spheria,L.cordata,?-complex variant type,including L.gemmiforma,L.fusiformis,L.dicrana,P.sicyoides,P.qinyuensis,L.fungorumis sp.nov,?-rapid shrinkage type,including L.ovalis,L.qingboikonensis,?-simple elongated type,including L.elongata,?-complex elongated type,including L.foliolatusa,P.oblong,L.ellipticulum,P.longfurumis sp.nov.This conclusion provides the basis for the study of Longfengshaniaceae morphology and evolution.3.With the quantitative statistical analysis of modern morphology,combined with the spatio-temporal succession,we build the early simple macroalgae evolution model.Phytoplankton Chuariaceae is first appeared,in the Mesoproterozoic era,then the macroalgea diffenrentiated Tawuiaceae,both were prosperous in Tonian,Neoproterozoic,and the latter appeared specialized J,C,U-shaped individuals in some regions.As the continual oxygenate and structure changes of pleaosea,the first radiation evolution of macroalgae was observed in Tonian,and Benthic fixation macroalage-Longfengshaniaceae occurred.The evolution model can be classfied into no-complicate elongation,which from I-simple basic type to ?-complex variant type,and,elongate and complication,that from ?-rapid shrinkage type,then ?-simple elongated type,to ?-complex elongated type.But productivity is low,macrophages are mainly dominated by nobranching large leaves or solid spheres.With the further improvement of the sea environment,when it comes to Edicacan oen,the filiform(Anhuiphyton),filose(Enteromorphites),thin-strip(Baculiphyca),fasciculate(Doushantuophyton)branching leaf benthic fixation macroalgae had appeared.4.According to the characteristics of macroscopic algal biogeographic distribution in Tonian,the author think There is a macroscopical algal realm in the lower latitudes near the equator.,and it can be further divided into the NorthChina-Lauren(Chuaria-Tawuia-Longfengshania)region and the Yangzi-India(ChuariaTawuia)region.According to the biological characteristics,it can be divided into NorthChina macroalgae province and Lauren macroalgae province,the former can be divided into central Yanshan benthic-plankton zone and the edge Huainan,Liaonan plankton zone,the latter into center McKenzie benthic-plankton zone and VictoraUtah plankton zone.However,in the Yangzi-India(Chuaria-Tawuia)region,the species distribution is basically the same,only the macrophytoplankton.The macroalgae distribution are controlled by two factors: ancient latitude and paleogeographic isolation.According to the paleobiogeographic division of macroalgae above,during Rodinia period of Neoproterozoic era,it can be sure that North China plate is contiguous with the north edge of Laurentian,both are in the eastern edge of the Rodinia Supercontinent,and The Yangtze plate is adjacent to the Indian ancient land,located on the western edge of the Supercontinent.5.Based on the analysis of rock strata,BSR activity and its influencing factors,it is preliminarily believed the longfengshan section is rich in the fossil-level pyrite,which is mostly biogenic.Combined with the feature of mineral analysis and fossil buried characters,the author think the authigenic clay mineral,that with the carbonaceous fossils,and microbial pyritization make good physical and chemical conditions for the preservation of Longfengshan biota.And with the distribution of sedimentary pyrite particle size,the author think the living environment of the organism is hypoxia-secondary oxidation.6.Based on the results of SEM observation on microregion of fossils,the author review the microstructure of Chuaria,including cell membrane,wall and channel exsitd on the face and interlamination,that found before.Lenticular dense electronic fine lines,found in the carbonaceous interior of Longfengshania,observed by SEM,and fiber struture,exsite in the stem-like of Longfengshania,found by peel method,make the new evidence for the Eukaryotic multicellular ownership of Longfengshania.However,the concentric pattern or wrinkle structure on the surface Chuaria,Tawuia,Longfengshania,should be the results of buried,are not protogenesis structures of the thallus. |
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