埃迪卡拉纪疑难化石Shaanxilithes在云南王家湾剖面的发现及地层意义

PROBLEMATIC EDIACARAN FOSSIL SHAANXILITHESFROM THE JIUCHENG MEMBER OF WANGJIAWAN SECTION IN JINNING,YUNNAN PROVINCE

Shaanxilithes是一类广泛分布于埃迪卡拉纪地层中的疑难化石,其重复而边缘模糊的圆盘状单元体、简单的躯体构型以及缺乏有效的对比化石给确立其生物亲缘关系带来很大的困难。本文报道了云南晋宁六街镇三印村渔户村组旧城段发现的大量保存精美化石——宁强陕西迹(Shaanxilithes ningqiangensis)。通过形态学及精细的显微结构观察表明Shaanxilithes具有稳定的形态结构,外形呈带状,由许多紧密相连的圆盘状结构组成,是一类不同于遗迹化石的实体化石。随着研究地区的扩大,Shaanxilithes相继在扬子板块的陕南、黔中、川北地区,华北板块的青海、宁夏以及西伯利亚和印度西北边缘埃迪卡拉纪晚期地层中发现和报道。此次Shaanxilithes在滇东晋宁地区的大量发现进一步表明此类化石有更广泛的地理分布,揭示了其重要的古生物地层意义,表明Shaanxilithes不仅是区域间而且是洲际之间埃迪卡拉纪晚期地层对比的潜在标准化石。依据形态学分析,结合埋藏学信息,文中对Shaanxilithes的生物属性以及谱系关系进行了讨论,为理解从埃迪卡拉纪晚期到早寒武世古生物学特征的演化带来新的启示。

Dozens of exquisitely preserved Ediacaran problematic fossils Shaanxilithes are collected from the Jiucheng Member of the Wangjiawan Section,in Jinning,Yunnan.Although the simple body comprising a series of repetitive discoids with irregular margins and lacking comparable analogues make it difficult to refer Shaanxilithes to a group with a certain taxonomic affinity,morphological and microstructural investigation of the collected samples excludes Shaanxilthes ningqiangensis from trace fossils.Observation of the new fossils demonstrates that the fossils of Shaanxilithes are body fossils,characterized by a stable shape and form of three dimensionally preserved ribbons and discoidal units.Until now,the extensive biogeographical distribution of S.ningqiangensis in eastern Yunnan,southern Shaanxi,Northern Sichuan,Central Guizhou,Northwestern Qinghai,Northern Ningxia of China,and North-central part of Siberia,as well as the Lesser Himalaya of India suggests S.ningqiangensis is a cosmopolitan species of the genera.The significant biostratigraphy of S.ningqiangensis demonstrates that,it can not only be a potential index fossil of Ediacaran age,but can also cast new insight into our understanding of the biological diversity precluding the Cambrian Explosion.