New Benthic Fossils from the Late Ediacaran Strata of Southwestern China

The Jiangchuan Biota from the Jiucheng Member(Mb.)of the Dengying Formation(Fm.),discovered in Jiangchuan,eastern Yunnan,China,is marked by copious macrofossils at the apex of the Ediacaran strata.This fauna features benthic algae with varied holdfasts and other fossils of indeterminate taxonomic affinity and is compositionally unique compared to the Shibantan and Gaojiashan biotas of the Dengying Fm.and the Miaohe and Wenghui biotas of the Doushantuo Fm.,elsewhere in China.One novel benthic saccular macroalgal fossil,named here Houjiashania yuxiensis gen.and sp.nov.,from the Jiangchuan Biota is based on fossils that are sausage-shaped,elongate,tubular,ranging from 0.3 to 4 cm in length,and up to 0.8 cm in diameter.One terminus is blunt and rounded to an obtuse angle,the other is bent with a spread-out surface resembling a holdfast,suggesting a three-dimensional thallus.Thin,stipe-shaped outgrowths,likely vestiges of sessile saccular life forms,are prevalent in macroalgal fossils of analogous size and shape,as well as present brown algae Scytosiphonaceae,such as Colpomenia and Dactylosiphon.The new findings augment the diversity of benthic algae,such as those known from the Early Neoproterozoic Longfengshan Biota in North China.The benthic algal macrofossils in the Jiucheng Mb.add to knowledge of Late Ediacaran metaphyte diversification and offer more clues about the evolutionary positioning of primitive macroalgae.The co-occurrence of numerous planktonic and benthic multicellular algae and planktonic microbes might have facilitated ecologically the more extensive later Cambrian explosion evidenced by the Chengjiang Biota in Yunnan.

华南滇东地区震旦(Ediacaran)系顶部Longfengshaniaceae藻类化石的发现及意义

本文报道了在中国云南东部晋宁、江川地区的震旦(Ediacaran)系顶部渔户村组旧城段新发现的龙凤山藻科(Longfengshaniaceae)化石,与华北燕山地区新元古代青白口系长龙山组及北美中元古代小达尔群产出的Longf engshania化石明显不同,叶状体形态更为多样,呈梭形、枣核形、铲形、长条带形或球囊形等,拟茎较粗壮,与叶状体的接合很平缓,部分可见盘状、短茎状、披针状固着构造和叶状体萌生现象。依据形态记述了2属6种,包括1新属2新种3相似种,讨论和修订了龙凤山藻的科、属特征。华南滇东地区这些宏体藻类化石的发现进一步表明震旦(Ediacaran)纪末期也存在后生植物的多样化发展,可能为早寒武世“澄江生物群”的爆发性演化奠定了生态基础。

滇东埃迪卡拉(震旦)系顶部旧城段多样宏体化石群的发现

在中国云南东部晋宁、江川地区的埃迪卡拉(震旦)系顶部灯影组旧城段,新发现了多样的宏体化石群,其中除了丰富的Vendotaenia与Tyrasotaenia类化石以外,以形体较大的Tawuia类和Longfengshaniaceae科等具固着构造的底栖多细胞藻类化石占据优势,另有一些形态奇特、亲缘关系不明的宏体化石,该组合与华南陡山沱组和灯影组石板滩段的宏体化石组合存在着明显的差别。依据形态特征,概述了部分产自江川旧城段的具有不同类型固着构造的底栖藻类和归属不明的宏体化石特征。滇东地区旧城段形态多样的宏体藻类化石的发现,进一步表明埃迪卡拉纪末期存在后生植物的多样化发展。这一时期浮游微生物和后生植物的共同繁盛可能为早寒武世"澄江生物群"的爆发奠定了生态基础。

A New Diverse Macrofossil Lagersttte from the Uppermost Ediacaran of Southwestern China

A new macrofossil Lagerstatte was discovered from the uppermost Ediacaran Jiucheng Member at Jinning and Jiangchuan of the eastern Yunnan, yielding numerous diverse well-preserved thallophyte macrofossils. These include the previously-known representatives of vendobionts, Vendotaenia and Tyrasotaenia, and the biggish multicellular benthos such as Chuaria-like and Tawuia- like fossiis, as well as Longfengshaniaceaens with diverse holdfast structures. There are still some other problematic macrofossils with peculiar configurations as well as uncertain relatives. The distinct dominance of the giant, unbranching thallophytes occasionally with holdfast structures distinguishes this assemblage from the other Ediacaran macrofossil Lagerstattes in the Doushantuo Formation at Miaohe, Wenghui and Lantian, and the contemporary assemblage in the Shibantan Member of Dengying Formation, Yangtze Gorges area. This paper outlines the characteristics of some of the multicellular macrofossils from the Jiucheng Member at Jiangchuan. They include some macrofossils with different types of holdfast structure, larger Chuaria-like and Tawuia-like morphology and questionable affinities as well. The discovery of greater diverse macrofossil assemblages from the Jiucheng Member of eastern Yunnan has further indicated that an important diversification and evolutionary radiation of metaphytes took place in the latest Ediacaran time. This radiation of largescale, benthic metaphyte along with phytoplankton was likely important contributors to the early Cambrian explosion of metazoans.

云南东部江川生物群中的香肠状疑难化石——Tawuia化石属性的新解释

云南东部伊迪卡拉(震旦)系顶部灯影组旧城段的江川生物群是华南又一大类丰富且多样化的宏体化石群,其以碳质压膜的方式保存。在该生物群中,我们发现大量香肠状碳质压膜的宏体化石,与成冰(南华)纪全球大冰期之前中、新元古代地层中广泛分布的Tawuia碳膜化石的大小、形态非常相似。其最大宽度达4.5 mm,最大长度可达4 cm,长宽比均>2,膜面光滑,未见其他稳定纹饰,有的化石标本边缘碳质保存较多,可见深黑色边缘环带。但部分化石保存的形态与常见的直棒状I形、U形、C形Tawuia化石相比却较为特殊,呈现直角L形、8字形、宽U形、环状O形等多种保存形态,个别标本弯折部位可见明显的碳质增厚和横脊纹残留,边缘残存有大小不一的刺状突起构造。这类特异形态保存的似Tawuia化石显然不能解释为以往较为公认的浮游型叶状体藻类,而可能与冰期前的新元古代早期鲁西、淮南宏体化石群中的疑似蠕形动物亲缘的化石有传承关系。上述新发现的化石形态表明:似Tawuia的碳膜宏体化石可能是多源属性的早期多细胞生物。其中短带至长带状叶状体,可见短柄突起及疑似固着器构造的化石可确认为底栖宏体藻类;多数的叶状体推测为香肠状或长囊状,生活史中包含远洋浮游的类型,可能归属于原始不分枝的多核体藻类或早期分化出的中空囊状的多细胞藻类;本文展示的部分规则变形的似Tawuia化石,更可能是两侧对称动物亲缘的,生活于近海的底栖生物体发生主动扭曲后,被特异埋藏所呈现出的特殊保存形态,而随机浮游或表栖的多细胞藻类死亡沉积时不会形成类似形态的化石。

埃迪卡拉纪晚期疑难化石Shaanxilithes在云南会泽朱家箐剖面的首现及其意义

陕西迹(Shaanxilithes)见证了埃迪卡拉纪–寒武纪之交生物演化及生态环境的变化,是埃迪卡拉纪末期标志性的疑难化石,具有全球对比意义。本文首次报道了云南曲靖会泽县大海乡朱家箐剖面灯影组旧城段泥质灰岩中新发现的宁强陕西迹(Shaanxilithes ningqiangensis Xing,Yue and Zhang,1984)。所采集的标本整体形态上呈条带状,边缘呈锯齿状参差不齐,可见环状体分布。通过镜下观察,可发现散落圆盘状单元。将大海乡朱家箐剖面与晋宁六街镇王家湾剖面渔户村组旧城段所产出的Shaanxilithes化石对比后发现,朱家箐剖面的标本宽度更窄,长度更长,碎片化更加明显。通过微区X射线荧光光谱仪(μ-XRF)将朱家箐剖面和王家湾剖面的标本进行对比分析后可知,前者形态在Si、Al、K的元素分布图中显示清晰,而后者的形态主要体现在Fe元素的分布图上;前者化石和围岩中Ca元素的含量远远高于后者;S元素仅在前者存在微量的分布,在后者中未有信号显示。新的化石证据表明Shaanxilithes并非只产出自碎屑岩中,还可以在灰岩中保存。化石μ-XRF的面扫描和半定量分析表明Shaanxilithes可能为伊利石矿物交代,并且说明在不同岩相背景下,风化作用程度的强弱造成两个产地化石的差异性保存。随着研究区域不断扩大,Shaanxilithes相继在华南板块滇东地区、印度西北缘、纳米比亚、华北板块西南缘等地区晚埃迪卡拉世地层中被发现。此次在滇东会泽地区发现的Shaanxilithes,进一步表明该化石分布的广泛性,可作为全球晚埃迪卡拉世地层对比的标准化石。本文结合形态学分析和微区X射线荧光光谱分析,讨论了Shaanxilithes的埋藏学信息与亲缘关系,为探索埃迪卡拉纪–寒武纪过渡时期的生物和生态特征提供了更多视角。