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鲎虫从早石炭世延续至今,它的分类特征没有发生明显变化,被认为是“一个演化呆滞的类群”。笔者在陕西宜君地区马庄剖面发现了延长组长7段底部地层中保存的鲎虫化石,新标本保存了较好的小颚腺凸起结构,其为鲎虫的排泄器官,鉴于前人对哈萨克虫的研究定义,小颚腺可以作为鉴别鲎虫的重要特征。鲎虫的生存特性,结合同层位发现的膜翅类昆虫化石和底栖宏观藻类化石,都证明鄂尔多斯盆地南部宜君地区延长组长7段沉积初期水体深度很浅,为淡水环境。长7段是延长组沉积的最大湖泛期,在盆地南部宜君地区湖盆面积的扩张和水体的加深在长7段沉积初期尚未开始。本研究的发现对评估长7段湖泛期水体深度、水域面积和烃源岩分布范围具有重要意义。
From the early Carboniferous to the present, pinworm has not changed significantly in its taxonomic characteristics and is considered as “an evolved sluggish population.” The author found in the section of Mazhuang, Yijun, Shaanxi province, the extension of the foraminifera preserved in the bottom strata of the 7th member of the group leader. The new specimen preserved a good structure of mandibular gland protuberance, which is the excretory organ of pinworm. The definition of Kazakh worms, the mandibular gland can be used as an important feature to identify pinworms. The survival characteristics of the pinworm, together with the phylum of the genus Hymenoptera and the macrobenthic fossils of macrobenthos found in the same layer, all proved that the depth of the water body in the early 7 member of Yanchang Formation in the Yijun area in the southern Ordos Basin is very shallow and is a freshwater environment. The Chang 7 Member is the largest lacustrine period of Yanchang Formation sedimentation. The expansion of lake basin and deepening of water body in Yijun area in the southern part of the basin did not start at the beginning of the deposition of Chang 7 Member. The findings of this study are of great significance to evaluate the water depth, water area and source rock distribution of the Chang 7 Member during the flood season.