摘要
前寒武纪真核生物的细胞形态和超微结构的证据评价问题,已成为当前国际上地质古生物学家激烈而持久争论的焦点。克劳德(P.E.Cloud)等根据大气层中多量氧的积累开始于18—20亿年这一间接资料,推论需氧的真核生物只能出现在20亿年之后的观点,从理论上给了人们以重要的启迪。
This paper describes eight species and one undetermined species of the microfossil green algae and blue-green algae belonging to six genera discovered from the Wumishah Formation(ca.1200—1400m.y.old)of Jixian County.Of these,Hyalothecopsis sinica gen.et sp.nov.,H.nanshanensis gen.et sp.nov.and Uronemopsis tenuis gen.et sp.nov.,are considered as green algae,wbile Oscillatoriopsis acuta sp.nov.,O.formosa sp.nov.,O.doliocellularis sp.nov.,Palaeoborzia cervicalis gen.et sp.nov.Palaeolyngbya sp,and Saccolyngbya nanshanensis gen.et sp.nov.,are considered as blue-green algae.The new green algae discovered provide an important paleontological evidence for the orgin on the earth of eucaryotic organisms.Phylum Chlorophyta Family DesmidiaceaeⅠHyalothecopsis Zhang,gen.nov.Type species:Hyalothecopsis sinica gen.et sp.nov.Cells joined end to end in unbranched filaments;cells shorter than wide,with a distinct but shallow median constriction;semieells trapezoidal or oblong in front view.Two species discovered:1.H.sinica Zhang,gen.et sp.nov.(Pl.Ⅰ,fig.1)Cells 19—21μm broad,about 13μm long;sinus shallow and narrow;semicells trapezoidal in front view.Type specimen:80606—52.H.nanshanensis Zhang,gen.et sp.nov.(PlⅠ,fig.2)Cells 15—17μm broad,8—10μm long;sinus shallow and somewhat open outward;semicells narrowly oblong in front view;cells content of same material which is brown in color.Type specimen:80606—46Family UlotrichaceaeⅡ.Uronemopsis Zhang,gen.nov.Type species:Uronemopsis tenuis gen.et sp.nov.Filament unbranched;cells about as long as wide;the upper part of apical cell acuminate,basal part expanded.Only one species discovered:U.tenuis Zhang,gen.et sp.nov.(Pl.Ⅰ,fig.3)Filament long;apical cell about 5μm long,lower part expanded,upper part pointed;cells 5—6.3μm in diameter,5—7.5μm long;slightly constricted at the cross-walls or not.Type specimen:80606—2Phylum CyanophytaFamily OscillatoriaceaeⅢ.Oscillatariopsis Schopf,1968Explanation:In the identification,any trichomes unbranched,sheath absent,constricted or not constricted at the cross-walls;cells disc-shaped or cylindrical.1.O.acuta Zhang,sp.nov.(Pl.Ⅰ,figs.4a,4b)Trichome slightly curved;slightly tapering toward the apex;apical cell broadly conical,with a sharp-pointed apex;cells disc-shaped,10—11μm broad,5—6μm long;evidently constricted at the crosswalls.Type specimen:80606—292.O.formosa Zhang,sp.nov.(Pl.Ⅰ,fig.9)Tricbome slightly curved;apical cell broadly rounded;cells disc-shaped,13—14μm broad,6.3—7.5μm long;not constricted at the cross-walls.Type specimen:79606a3.O.doliocellularis Zhang,sp.nov.(Pl.Ⅰ,fig.6)Trichome straight;tapering toward the apex;apical cell ovoid;cells barrel-shaped,7.5—11.3μm broad,6.3—11.31μm long.Type specimen:79605f—2Ⅳ.Palaeaborzia Zhang,gen.nov.Type species:Palaeoborizia cervicalis gen.et sp.nov.Trichome short,containing a few cells;one end a little narrower than the other;slightly constricted at cross-walls;apical cell broadly rounded;sheath absent.Only one species discovered:P.cervicalis Zhang,gen.et sp.nov.(Pl.Ⅰ,fig.7)Cells 23—25μm broad,3.8—6.3μm other features same as those for genus.Type specimen:79606B—1Ⅴ.Palaeolyngbya Schopf,1968 Palaeolyngbya sp.(Pl.Ⅰ,fig.5)Filament straight,45μm in diameter,sheath thick;trichome solitary,cells 15—20μm broad,10—12.5μm long;with or without constriction at the cross-walls;apical cell unseen.Because no apical cell Seen,the species can not be identified.Type specimen:80606—24Ⅵ.Saccalyngbya Zhang,gen.nov.Type species:Sacaolyngbya qingshanensis gen.et sp.nov.Trichome short,unbranched,the same diameter throughout;the fragments of degraded uniserial trichome surrounded by a wide sheathi;sheath oblong-elliptic,gradually attenuated from the middle to the rounded-truncated apices,with a distinct median constriction,dividing the plant into two similar parts;sheath colorless,with fine and slightly constricted transverse striations.Only one species discovered:Saccolyngbya qingshanensis Zhang,gen.et sp.nov.(Pl.Ⅰ,fig.8a)Plant 15μm broad,101μm long;the fragments of degraded uniserial trichome irregularly distributed in sheath;cells disc-shaped,3—4μm broad,about 1μm long;apical cell broadly rounded;otherwise as in the genus.Type specimen:780207.
作者
张鹏远
Zhang Pengyuan(Tianjin Institute of Geology and Minearal Resources,Chinese Academy of Geological Sciences)
出处
《地质学报》
1982年第1期34-41,91,共9页
Acta Geologica Sinica
