【摘要】 陕南寒武纪梅树村期西乡生物群中的管状化石数量丰富,本文对其中的三类主要化石类型:软舌螺、似软舌螺类和阿纳巴管类进行了深入研究。其中软舌螺主要为圆管螺目,属于寒武纪软舌螺演化的第一阶段,且化石具有不同的壳体结构:主要分为单层壳和多层壳两大类,多层壳根据截面又可分为同心与偏心两类。单层壳与同心多层壳可能属于原生结构;偏心多层壳属于次生结构。对上述各类结构进行了分类统计,其中的单层壳与次生多层壳居多,并推测原生多层壳体的出现可加固管体,是地球早期生物为应对同期食肉动物所进化出的生存对策。似软舌螺类的两属:小软舌螺属及小钻孔螺属在此生物群中均有发现。西乡生物群中的阿纳巴管类主要为Anabarites trisulcatus,Aculeochrea tripartitus和Anabarites isiticus,其中Anabarites isiticus的化石壳体表面具有细密生长纹,生长纹可明显分为较粗与较细两类,二者相间排列、重复出现,体现了生物不同的生长周期。更多还原

【Abstract】 The Xixiang biota has a great amount of tubular fossils.This paper summarizes and describes three major types of them,including hyoliths,hyolithelminths and anabaritids.The hyoliths in this biota belong mainly to Circothecida and are considered as the first stage of Cambrian hyoliths evolution.These hyoliths have different kinds of skeletal structures,which could be divided into unilaminar shells and multilayered shells.The multilayered shells could also be divided into concentric kind and eccentric kind.The unilaminar shells and the concentric multilayered shells are likely to be native,and the eccentric multilayered shells are likely to be diagenetic.Statistical results show that unilaminar shells and eccentric multilayered shells are predominate.The occurrence of the multilayered shells may provide extra protection for early organisms on earth,helping them to survive from their predators.Then,the Hyolithellus and Torellellaall found in this biota.Anabaritids of the Xixiang biota are mainly Anabarites trisulcatus,Anabarites tripartitus and Anabarites isiticus.Among them,Anabarites isiticus has closely arranged growth striations which could be divided into two types by their width.These narrow or wide types arrange in alternate and repeated,which indicates a different growth cycle of organisms.更多还原