湖北宜昌乔家坪村寒武系水井沱组海绵动物化石群

A sponge fossil fauna from the Cambrian Shuijingtuo Formation, Qiaojiaping Village, Yichang, Hubei Province

海绵动物是最原始的动物门类之一,其演化史对于研究多细胞动物的起源和早期演化至关重要。现有的化石记录显示,水体较深的贫氧环境可能是寒武纪早期海绵动物演化的重要场所之一。前人在贵州、湖南、安徽等多地的斜坡至盆地相黑色页岩中已经报道了数个海绵化石群。在这样的环境中,由于水动力作用较弱,海绵骨架结构容易得到原位保存。湖北宜昌秭归乔家坪村剖面的水井沱组为一套寒武系第三阶的台内凹陷沉积。本文描述在此剖面顶部发现的一个海绵动物化石群,其中包含Palaeosaccus minus sp.nov.、Triticispongia giganta sp.nov.、Triticispongia cf.diagonata、Sanshapentella dapingi、?Wapkia sp.以及三类分类未定的海绵动物化石,共8类,分属至少4个属。其中Triticispongia和Sanshapentella也常见于前人报道的多个同时期深水相海绵动物化石群。除此以外,作者还识别出了三种根束类型。水井沱组海绵动物化石群所呈现出的形态多样性进一步佐证了在寒武纪大爆发期间,至515 Ma左右,海绵动物已成功适应多种环境,且繁盛于水体较深、大多数动物难以生存的贫氧环境。

Sponges are one of the most basic lineages among all animal lives.Their early evolutionary history is key to understanding the origin and early evolution of the whole kingdom Animalia.As indicated by the known fossil record,the relatively deep,dysoxic environment may have been an important domain for the early evolution of the phylum Porifera.Early Cambrian sponge fossil faunas have been reported from slope to basinal black shales of multiple localities in South China.The static hydrodynamic setting in such environments enables intact preservation of the sponge skeletal frame.The Shuijingtuo Formation at the Qiaojiaping Village represents an intra-platform basin during the Cambrian Age 3.A diversified sponge fossil fauna is here described from the top of this formation,with fossils including Palaeosaccus minus sp.nov.,Triticispongia giganta sp.nov.,Triticispongia cf.diagonata,Sanshapentella dapingi,?Wapkia sp.,and three taxonomically undetermined forms.Among them,Triticispongia and Sanshapentella seem to be universal taxa in coeval deep water sponge faunas in South China.In addition,three types of root tufts are described.The morphological diversity of this fossil fauna enhances the concept that sponges have been successful and prosperous in relatively deep,dysoxic environments that most animals could not survive by approximately 515 Ma.