陕西西乡灯影组顶部的瓶状微化石

VASE-SHAPED MICROFOSSILS FROM TOP OF THE TONGYING FORMATION IN XIXIANG, SHAANXI

瓶状微化石被认为是某种未知海相原生动物外壳化石,最早出现于900—850Ma以前。本文记述的该类化石,产自陕西西乡三郎铺小湾里下寒武统灯影组顶部杨家沟段,相当于梅树村阶中—上部,计10属、13种和2未定种(含6新属、9新种)。所获化石个体数量及形态类型丰富,保存良好,并见有大量具公共壳壁的连体壳。此类连体壳的连接程度呈系列变化,可能代表处于分裂状态的生物体,如是则可为其原生动物解释提供一佐证。瓶状微化石在国外的地层分布限于晚前寒武系,我国是目前仅知的发现寒武纪瓶状微化石的国家。

The vase-shaped microfossils described here are collected from the top of the Tongying Formation, the Yangjiagou Member at Xiaowanli Village, Xixiang County, southernShaanxi. The age of the Yangjiagou Member which is still in dispute, has been assigned tothe Meishucunian or Chiungchussu Age by different authors. Based on analysis of the smallshelly fossil assemblage associated with the vase-shaped microfossils within the Yangjiagou Member, the authors consider that the Yangjiagou Member should be correlated with thestrata yielding the small shelly fossil Paragloborilus--Siphogonuchites and Sinosachites--Lap-worthella Zones of the Meishucun section, Yunnan. These vase--shaped microfossils, generally regarded as a kind of marine protozoans,have been found from the Late Precambrian abroad, with maximum isotopic ages up to900Ma. In China, however, such microfossils occur not only in the Late Precambrian, butalso in the Early Cambrian Meishucunian Stage, indicating that so far as known, China is theonly ocality throughout the whole world where the Cambrian. vase-shaped microfossils have been found. These microfossils from the Yangjiagou Member are abundant and diversified.In addition, a large number of specimens with two or more tests of the vase-shaped microorganisms combined with a common wall are found. Such forms might be in a certain conditionof schizogenesis. A total of 10 genera and 15 specise are identified, including 6 new genera and 9 new species.