贵州剑河八郎寒武系清虚洞组的楔叶形虫Sphenothallus Hall,1847

贵州剑河八郎松山寒武系黔东统中部清虚洞组主要由灰岩、泥岩组成,下部以灰岩为主,上部为泥岩、灰岩互层,顶部为中层白云岩。上部含有大量的褶颊虫类和掘头虫类三叶虫及带软躯体动物多门类化石组合。本文报道的楔叶形虫Sphenothallus Hall,1847产于清虚洞组上部,分异度低,仅1属1相似种,即台江楔叶形虫(相似种)Sphenothallus cf.taijiangensis Zhu et al.,2000,位于Redlichia(R.)guizhouensis-Redlichia(R.)nobilis顶峰带。S.cf.taijiangensis化石保存较好,少数标本管壁之间保存有横纹,说明Sphenothallus为一具有锥管状外壳的虫体。剑河八郎松山清虚洞组的楔叶形虫是贵州继牛蹄塘组、凯里组之后寒武系另一个产出层位,它的发现不仅丰富了清虚洞组生物群的组成,同时为全球楔叶形虫Sphenothallus的研究提供了新的材料。初步研究表明全球Sphenothallus的演化趋势是个体增长,管壁加厚物宽度变宽,口部膨胀角变小。Sphenothallus与现代刺胞动物水螅虫类或钵水母有密切关系。

SPHENOTHALLUS HALL,1847 FROM THE TSINGHSUTUNG FORMATION(QIANDONGIAN SERIES,CAMBRIAN)IN BALANG VILLAGE OF JIANHE COUNTY,GUIZHOU PROVINCE,CHINA

The Tsinghsutung Formation(Qiandongian Series,Cambrian)of Songshan Section near Balang village,Jianhe County,Guizhou Province is mainly composed of limestone and mudstone,interbeded with mudstone and limestone in the upper part,and medium-bedded dolomite for the uppermost section.The upper part of the Tsinghsutung Formation belonging to the Redlichia(R.)guizhouensis-Redlichia(R.)nobilis Acme Zone is rich in ptychopariids,trilonites,mollusks and other invertebrate fossils including a few soft-body fossils.So far only 1 species,Sphenothallus cf.taijiangensis Zhu et al.,2000 has been found in this zone.A few well-preserved fossil specimens are described here with obvious annulations on the wall tube,indicating the Sphenothallus had conical-tubular skeleton.Sphenothallusfrom the Tsinghsutung Formation not only enriches the assemblage of the Tsinghsutung Formation biota,but also provides new material for the research of Sphenothallus.The preliminary study shows that a evolutionary trend exists for the lengthening individuals,widening longtitudinal thickenings,and diminishing apertual expandings.The Sphenothallus have affinities with polypoid hydrozoans or scyphozoans.