湖南花垣中寒武世晚期开腔骨类化石

Chancelloriids from Late Middle Cambrian of Huayuan,Hunan,South China

记述了湖南花垣县排碧剖面寒武系花桥组上部灰岩中的开腔骨类化石。 4 0余块形态多样的化石标本 ,包括具 6 - 7+1型的Chancelloriaaltaica ;4 +0型Archiasterellasp .;和 3+0型Allonniasp .;以及形态奇特的开腔骨针Chancelloriasp .,与三叶虫、牙形石、腕足动物、软舌螺类等共生 ,时代属中寒武世晚期。与其他研究比较证明 ,这是迄今我国中寒武世晚期开腔骨类最高产出层位 ,也是世界上少数几个开腔骨类较高的产出层位之一。通过对开腔骨类骨片构造、保存环境及其地史地理分布的分析 ,认为开腔骨类是一类与海绵类有密切关系、已绝灭的后生动物 ,是一类生活于浅海环境的底栖固着型生物。

The Chancelloriids were recovered from dark grey thin-bedded micrites and bioclastic micrites of the upper Middle Cambrian Huaqiao Formation at the Paibi section in Huayuan County,Hunan Province,China.About 40 samples with diverse sclerites have been identified,including Chancelloria altaica with 6-7+1 ray patterns,Archiasterlla sp.with 4+0 ray patterns and Allonnia sp.with 3+0 ray patterns as well as Chancelloria sp.with peculiar sclerite patterns.In addition to chancelloriids,these chancelloriid-bearing rocks,yield abundant and diverse trilobites,conodonts,hyolithids,hyolithellids,brachiopods,sponge spicules and ornamented tubular fossils.Compared with the materials reported from the Cambrian of Australia,Northwestern Canada,Western Argentina,West Africa and Iran etc.,it is indicated that the Hunan assemblage is the latest records of Middle Cambrian chancelloriids in China and is one of a few higher horizons of occurrence of chancelloriids recovered in the world.Based on analysis of sclerite structure,preservation and the stratigraphic distributions of chancelloriids,the authors support the opinion that the chancelloriid may belong to a group of extinct metazoans which is closer to Porifera,in the systematic phylogenetic position.It probably represents a sessile animal which adapted to shallow sea environments.